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Open Access

Peer-reviewed

Research Article

Detection of Helminth Eggs and Identification of Hookworm Species in Stray Cats, Dogs and Soil from Klang Valley, Malaysia

  • Sandee Tun ,

    Contributed equally to this work with: Sandee Tun, Init Ithoi

    Affiliation Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯
  • Init Ithoi ,

    Contributed equally to this work with: Sandee Tun, Init Ithoi

    init@um.edu.my

    Affiliation Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯
  • Rohela Mahmud ,

    ‡ These authors also contributed equally to this work.

    Affiliation Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯
  • Nur Izyan Samsudin ,

    ‡ These authors also contributed equally to this work.

    Affiliation Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯
  • Chua Kek Heng ,

    ‡ These authors also contributed equally to this work.

    Affiliation Department of Biomedical Science, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯
  • Lau Yee Ling

    ‡ These authors also contributed equally to this work.

    Affiliation Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

    ⨯

Abstract

The present study was conducted to determine the prevalence of helminth eggs excreted in the faeces of stray cats, dogs and in soil samples. A total of 505 fresh samples of faeces (from 227 dogs and 152 cats) and soil were collected. The egg stage was detected via microscopy after the application of formalin–ether concentration technique. Genomic DNA was extracted from the samples containing hookworm eggs and used for further identification to the species level using real-time polymerase chain reaction coupled with high resolution melting analysis. Microscopic observation showed that the overall prevalence of helminth eggs among stray cats and dogs was 75.7% (95% CI = 71.2%–79.9%), in which 87.7% of dogs and 57.9% of cats were infected with at least one parasite genus. Five genera of heliminth eggs were detected in the faecal samples, including hookworms (46.4%), Toxocara (11.1%), Trichuris (8.4%), Spirometra (7.4%) and Ascaris (2.4%). The prevalence of helminth infections among stray dogs was significantly higher than that among stray cats (p < 0.001). Only three genera of helminths were detected in soil samples with the prevalence of 23% (95% CI = 15.1%–31%), consisting of hookworms (16.6%), Ascaris (4%) and Toxocara (2.4%). The molecular identification of hookworm species revealed that Ancylostoma ceylanicum was dominant in both faecal and soil samples. The dog hookworm, Ancylostoma caninum, was also detected among cats, which is the first such occurrence reported in Malaysia till date. This finding indicated that there was a cross-infection of A. caninum between stray cats and dogs because of their coexistent within human communities. Taken together, these data suggest the potential role of stray cats and dogs as being the main sources of environmental contamination as well as for human infections.

Citation: Tun S, Ithoi I, Mahmud R, Samsudin NI, Kek Heng C, Ling LY (2015) Detection of Helminth Eggs and Identification of Hookworm Species in Stray Cats, Dogs and Soil from Klang Valley, Malaysia. PLoS ONE 10(12): e0142231. https://doi.org/10.1371/journal.pone.0142231

Editor: Emmanuel Serrano Ferron, Universidade de Aveiro, PORTUGAL

Received: July 24, 2015; Accepted: October 18, 2015; Published: December 15, 2015

Copyright: © 2015 Tun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Data Availability: All relevant data are within the paper and its Supporting Information file.

Funding: This study was supported by University of Malaya High Impact Research Grant HIR-MOHE (project UM.C/625/1/HIR/MOHE/MED/18). The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Cats and dogs are susceptible to and excellent carriers for many zoonotic helminth parasites, such as Ascaris lumbricoides, Ancylostoma ceylanicum, A. caninum, A. braziliense, Toxocara cati, T. canis, Trichuris vulpis and Spirometra species [1–17]. The behavioural characteristics of stray cats and dogs within a human environment, including defecating and scavenging rubbish, can easily lead to the contamination the soil within their roaming territories. Soil pollution with faecal materials is instrumental in transmission of soil-transmitted helminth (STH) infections. The fertilised eggs of STH (A. lumbricoides, Ancylostoma sp., Toxocara sp., T. vulpis, Toxascaris leonina, etc.) deposited in the soil develop rapidly and may reach an infective stage within a matter of weeks depending on environmental conditions. Because infected stray animals shed eggs around public places, healthy animals and humans may acquire infections due to the contaminated environments. Therefore, the zoonotic helminths are linked to soil contamination by free-roaming stray animals, which are sources of human infections. In Malaysia, there is little information on the prevalence of helminths among stray cats, dogs and in environmental soil samples. Zain et al. [18] reported that 74.6% of stray cats in Malaysia are infected with helminths. In addition, they reported hookworm species as being the most prevalent, including A. braziliense (30.8%) and A. ceylanicum (31.5%).

Hookworms are blood-feeding parasites that inhabit the intestine of mammalian hosts, including cats, dogs and humans. The most common hookworms in cats were identified as A. braziliense and A. ceylanicum, whereas those in dogs were identified as A. caninum and A. ceylanicum. In humans, two main species are prevalent, namely Necator americanus and Ancylostoma duodenale [19], coupled with zoonotic hookworms [20–22]. The clinical manifestations in humans include epigastric pain, diarrhoea and iron-deficiency anemia all of which can lead to malnutrition as well as mental and growth retardation, particularly in children [23–28]. Other manifestations, such as human eosinophilic enteritis (A. caninum) and cutaneous larva migrans or creeping eruptions (A. braziliense), have been found to predominantly be caused by a specific species of zoonotic hookworms [29–32].

Diagnosis of the helminth eggs by microscopic observation has been used for many decades [33]; however, molecular methods have achieved the best results for the identification of worm species. Several molecular studies have been carried out over the past few years to identify hookworm species, including conventional and semi-nested polymerase chain reaction (PCR) [22], single-strand conformation polymorphism [34], mutation scanning [35] and PCR–restriction fragment length polymorphism [36]. In the present study, real-time PCR with a high resolution melting analysis was used for the rapid detection and screening of hookworm species.

In Malaysia, a large populations of stray cats and dogs are seen roaming within human communities, and a close contact exists between people and these stray animals. Therefore, it would be useful to detect the existence of possible zoonotic parasites, particularly STH among these stray animals and soil samples from their faeces in polluted public parks where they roam freely. The establishment of STHs and hookworm species data is beneficial for public health services to devise effective control strategies and to raise awareness in local communities.

Materials and Methods

Sampling sites

The sampling sites were selected from within two animal shelters located in Klang Valley (latitude 3.139003 and longitude 101.686855) in the central-west region of Peninsular Malaysia. These were the Paws Animal Welfare Society (PAWS) at Subang and the Society for the Prevention of Cruelty to Animals (SPCA) at Ampang Jaya, which are located in the vicinity 15 km and 13 km from Kuala Lumpur city, respectively. Currently, PAWS and the SPCA are respectively homes to approximately 400 and 100 unwanted stray animals (cats and dogs) from Klang Valley (Kuala Lumpur and its adjoining areas in the state of Selangor). These stray cats and dogs were brought in by the workers (dog-catchers) of the Kuala Lumpur City Council.

The collection of soil samples was conducted at public places (bus stops, night markets, streets and children’s playgrounds) and three recreational parks, including the Kuala Lumpur Convention Centre (KLCC), the Kuala Lumpur Lake Garden and Taman Jaya Park of Petaling Jaya in Selangor (Table 1). The soil samples were collected at places frequented by stray cats and dogs, which can be a source of environmental contamination.

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Table 1. Location of the study areas in Klang Valley.

https://doi.org/10.1371/journal.pone.0142231.t001

Sample collection

The current study was conducted between April 2013 and September 2014. Three hundred and seventy-nine (379) faecal samples [152 (30%) from cats, 227 (45%) from dogs] and 126 (25%) soil samples were included in this study. The faecal samples were collected in wide-mouth screw-cap 100 ml clean faecal containers, which were properly labelled. The stray cats and dogs chosen in the current study were those newly targeted by the dog-catchers and that had not been treated by veterinarians previously. The fresh faecal samples were collected individually during the early morning (06.00–08.00) in the labelled containers with the assistance of the respective animal shelter workers. Subsequently, the soil samples were similarly collected during the morning (06.00–08.00) from moist areas within selected sampling sites. The leaves and debris on the surface of the soil were removed and approximately 200 to 250 g of soil from the surface (to 1 cm depth) was scraped off using a spoon-screw-capped. The collected samples were transported to the Department of Parasitology, Faculty of Medicine, University of Malaya, on the same day as collection and processed immediately or stored at 4°C for further microscopic observation. Furthermore, half of the faecal sample (from each container) was transferred to a new clean container and preserved with 2.5% potassium dichromate [22] in a ratio of one in three (1:3) parts, respectively, for further DNA extraction.

Formalin-ether concentration and microscopic observation

Approximately 1.5 g of faecal sample was placed into a clean paper cup containing 7 ml of 10% formal saline (27.0 ml of 37% formaldehyde in 73.0 ml of 0.85% sodium chloride) and stirred using a wooden stick to form a suspension (for soil, 50.0 g of sample was mixed with 14 ml of 10% formal saline to form the suspension). The suspension was strained through a wet gauze into a clean 15 ml test tube and, if necessary, adjusted to a total volume of 7 ml by topping up with 10% formal saline. Ether totalling 3 ml was then added to the suspension to make a total volume of 10 ml. The mixture was vigorously mixed for 1 to 2 min and then centrifuged for 5 min at 2,000 rpm. The centrifugation resulted in four layers comprising the top ether, a debris plug, formalin and sediment containing parasites at the bottom. The debris plug layer was freed from the sides of the tube with an applicator stick and the supernatant was decanted by inverting the centrifuge tube in one smooth motion. The sediment was withdrawn with a Pasteur pipette and mixed with a drop of iodine solution on a clean, dry microscope slide. The smear was covered with a coverslip and viewed under a light microscope using 10x, 20X and 40X magnifications for detecting the presence of helminth eggs. The morphology of the helminth eggs were confirmed by experienced parasitologists and were recorded to their specific genus.

Genomic DNA extraction

Extraction of genomic DNA was conducted for samples (either faecal or soil) that had been microscopically identified to be positive for hookworm eggs after formalin–ether concentration. The methanol-fixed samples, which had either a single infection (only hookworm eggs) or mixed infections with other helminth eggs, were individually subjected to DNA extraction using the PowerSoil DNA kit (catalog no. 12888–100; MO BIO Laboratories, Carlasbad, CA, USA), according to the manufacturer’s instructions. One modification of the final elution method for DNA was the use of 50 μl of elution buffer instead of 100 μl, as recommended by the manufacturer. The extracted DNA was stored at −20°C until further analysis.

The positive control DNA

The hookworm genomic DNA for positive controls, A. ceylanicum (JQ 673421.1) and A. caninum (JN 120882.1) [37] were kindly supplied by Dr. Romano Ngui from the Department of Parasitology, Faculty of Medicine, University of Malaya, Malaysia.

Real-time PCR assay–HRM analysis

Approximately 180–200 bp within the 5.8S and the second internal transcribed spacer (ITS-2) region of the hookworm ribosomal RNA was amplified by real-time PCR using a pair of degenerate primers UMF (forward: 5’-CACTGTTTGTCGAACGGYAC-3’) and UMR (reverse: 5’-AGTCSVKRRRCGATTMARCAG-3’) [37] and subsequently examined by HRM analysis. Real-time PCR was performed in a total reaction mixture of 20 μl containing 10 μl of MeltDoctor HRM Master Mix (Applied Biosystems, Inc., CA, USA), 10 pmole of each primer, approximately 10 ng/ml of genomic DNA and sterile deionized water using a 7500 Fast Real-Time PCR system (Applied Biosystems, Inc.). The control samples, which were the positive hookworm DNA [37] and negative (DNase free water, Sigma Cat. no. W4502), were additionally included in each PCR run. The PCR thermocycling condition was then conducted as previously described by Ngui et al. [37].

Statistical analyses

The data entry and statistical analyses were conducted using the Statistical Package for the Social Sciences (SPSS) software program for Windows version 2.2 (SPSS, Chicago, IL, USA). Pearson’s chi-square (x2) was carried out to test the differences of helminth infections based on egg secretion between stray cats and dogs. The level of statistical significance was set at p < 0.05 and for statistically significant factor, an odds ratio (OR) and 95% confidence interval (CI) were computed.

Ethical considerations

The protocol of the current study was reviewed and approved by the Institutional Animal Care and Use committee of the University of Malaya, Kuala Lumpur (Ethics Reference number: PAR/29/06/2012/II (R). Written permission was additionally obtained from the management authorities of the SPCA. Authorities of PAWS agreed verbally without any written permission. No permission was required for collection of soil samples as the data collection was not primarily for research but for the public health information. It was confirmed that our study did not involve endangered or protected species. The objectives and protocols of the research were thoroughly discussed with the authorities in charge.

Results

Helminth egg in faecal and soil samples detected by microscopy

From 379 faecal samples, 287 [75.7% (95% CI = 71.2%–79.9%)] were parasitized with at least one genus of helminth based on their excreted eggs. The prevalence of helminth eggs among stray dogs [87.7%, 199/227 (95% CI = 83.3%–91.6%) was significantly higher (p < 0.001, x2 = 43.9) than those of cats [57.9%, 88/152 (95% CI = 50%–65.8%)]. Both dogs and cats were infected with five genera of helminths, including hookworms (46.4%, 176/379), Toxocara (11.1%, 42/379), Trichuris (8.4%, 32/379), Spirometra (7.4%, 28/379) and Ascaris (2.4%, 9/379). The presence of helminth eggs in faecal samples among stray cats and dogs are summarised in Table 2.

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Table 2. Percentage of infected faecal samples among stray cats and dogs.

https://doi.org/10.1371/journal.pone.0142231.t002

Within the soil samples, 23% [29/126 (95% CI = 15.1%–31%)] of collected samples contained helminth eggs including hookworm (16.6%, 21/126), Ascaris (4%, 5/126) and Toxocara. (2.4%, 3/126).

Identification of hookworm species using real-time PCR–HRM analysis

All 197 microscopically positive samples for hookworm eggs (55 cats, 121 dogs, 21 soil samples) were successfully amplified by real-time PCR accompanied with high resolution melting analysis. Only two Ancylostoma sp., A. ceylanicum and A. caninum, were detected, as stated in Table 3. A. ceylanicum was detected to be dominant in samples from stray cats (29.6%, 45/152), dogs (44.5%, 101/227) and soil (14.3%, 18/126) as compared with A. caninum. Only a single species, either A. ceylanicum or A.caninum (no mixed infection), was detected in the current study (S1 Fig).

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Table 3. Prevalence of hookworm species in faecal and soil samples as detected by real-time polymerase chain reaction–high resolution melting analysis.

https://doi.org/10.1371/journal.pone.0142231.t003

Discussion

The sampling sites selected in the current study were situated in Klang Valley, the most developed region in Malaysia. This region is home to more than seven million people [38], largely for migrants from other states within Malaysia and also foreign workers (Indonesia, India, Bangladesh, Nepal and Myanmar). Additionally, it is home for many stray cats and dogs that roam public places, such as parks, night markets, street food-stalls, open restaurants and housing areas. Most of these animals are not sterilised, are left to reproduce, and therefore, the number of unwanted animals far exceeds the number of adoptions. Occasionally, these animals are captured by city council workers (dog-catchers) and are sent to animal welfare shelters (e.g. PAWS and SPCA); however, many remain in public areas and could potentially harbour zoonotic parasites. The results of the current study provide an insight into the zoonotic helminths that occur in domestic environments, potentially due to faecal contamination by infected stray cats and dogs.

Based on microscopic observation, 75.7% of the collected faecal samples were found to contain helminth eggs. The eggs were mostly of nematodes [hookworms (46.4%), Toxocara sp. (11.1%), Trichuris sp. (8.4%) and Ascaris sp. (2.4%)] and relatively few cestode [Spirometra sp. (7.4%)] worms. This finding is in agreement with other studies of cats and dogs, which noted a prevalence of infection of 61.9%and 88.6% [8, 22] in Malaysia, and these infections were dominated by nematode worms [8, 18]. On the other hand, in other countries, stray cats were reported to be mainly infective with cestode worms, comprising 97.6% of the total parasite load in Qatar [1] and 53.1% in Portugal [39]. This suggested that Malaysian stray cats and dogs are more prone to infections (with nematodes) from contaminated environmental soil than by consumption of infected paratenic hosts, such as fishes, frogs and birds. Further statistical analysis revealed that there was significantly (x2 = 43.9, p < 0.001) more stray dogs (87.7%) being infected with helminths than stray cats (57.9%), among which hookworm was the most prevalent helminth. Similar observations were additionally reported in several surveys among cats and dogs, including in Thailand [13, 40], Cambodia [20], India [41], Brazil [42], Venezuela [43] and Costa Rica [44].

Subsequently, Toxocara sp. (11.1%) was the second most prevalent in faecal samples from both stray cats and dogs. Among dogs, a prevalence of 11.9% was found (known as T. canis) and 9.9% prevalence was identified among cats (known as T. cati). These results showed that the prevalence of Toxocara sp. in the current study was higher than that reported among cats and dogs in Thailand (3.5%) [14], India (4%) [45] and Brazil (5.5%) [46]. In particular, among faecal samples of cats, our results were similar to that of a report from Egypt (9%) [15] but contrasted with reports from Denmark (79%) [47], Iran (78%) [48] and Spain (55.2%) [6].

The third most common helminth detected in the current study was Trichuris sp., found to be higher among stray dogs (11%) as compared to stray cats (2%) which was in agreement with a previous study in Malaysia [8]. Among cats, Trichuris sp. in the current study was noted to be higher than in Japan (0.2%) [49] but lower than those in West India (71%) [45]. Due to large similarities in morphology, Trichuris eggs detected in the current study represent either T. trichura or T. vulpis, which requires further molecular identification into species level to resolve.

Ascaris sp. eggs that resembled A. lumbricoides (human origin) were additionally detected in samples from stray dogs (7.9%), cats (0.7%) and soil (4%). Stray dogs were reported to be the reservoirs and environmental contaminators of Ascaris sp. eggs around the communities [50]. Furthermore, the DNA extracted from Ascaris sp. eggs (from dogs) was found to be of 100% homology to those of A. lumbricoides obtained from humans [51]. Therefore, the current finding may be due to environmental contamination in which stray cats/dogs probably act as reservoirs of ascariasis in human populations.

The eggs of Spirometra sp. were found in faecal samples of both stray cats (9.2%) and dogs (3.5%). In the previous study performed in Malaysia, Spirometra sp. was noted to be absent among stray cats [18], and surprisingly, the prevalence of Spirometra sp. found in the current study was higher than that in cats reported from Shiraz, Iran (3.8%) [52] and New York, USA (0.4%) [53]. The detection of helminths in the infected hosts, solely based on the finding of eggs in faecal samples may contain disadvantages such as being missed or undetectable in cases of low infections. The detection of infection by post-mortem has the advantage over faecal-egg examination due to the accessibility of the helminths directly from the animals; however, it is unethical to sacrifice animals to detect the infective helminths. Thus, the degree of helminth infections in the current study may be higher than currently reported, as only infections by matured helminths that are capable of producing eggs were counted.

Among soil samples, 23% were found to be positive for helminth eggs, which was in accordance with the previous studies conducted in Malaysia (26.7%) [54] and in Montreal (25.6%) [55], but lower than in Turkey (84.4%) [56]. Variations in the distribution of these helminths is highly dependent on the climate and the environment factors that favour the survival of the helminth eggs, as well as personal hygiene, diet and exposure to the susceptible animals. Since Malaysia is a tropical country with hot and humid weather, the transmission of helminths from the soil is favourable (16.6% hookworms, 4% Ascaris sp. and 2.4% Toxocara sp.), particularly in the areas where stray cats and dogs are common.

Contamination with Toxocara eggs in soil samples from public areas was noted within various countries, such as Spain (36.4%) [57], Italy (63.6%) [58], Turkey (30.6%) [59] and Malaysia (12.1%) [54]. In addition, the contamination of soil by infective Toxocara eggs was seen to be proportional with the prevalence of human toxocariasis; hence, Toxocara sp. was noted to be among the important parasites in public health [60]. However, Toxocara eggs found in the current study can additionally be from another new variant of Toxocara species, T. malaysiensis [61, 62]. Consequently, cross-infection might have occurred among these stray animals, although T. canis and T. cati were known to be dog and cat nematodes, respectively.

The identification of helminths based on the morphology of the eggs can be satisfied up to the genus level, and the method has been used within parasitology laboratories for diagnosis purposes for many decades. Morphological observations coupled with molecular techniques have been found to be the best methods to identify the parasite species to date. Thus, our subsequent report was the identification of hookworm species using real-time PCR coupled with high resolution melting analysis. All samples from dogs (121), cats (55) and soil (21) that were microscopically positive for hookworm eggs were successfully analysed revealing two species, namely A. ceylanicum and A. caninum. A. ceylanicum was found to be more prevalent than A. caninum and was commonly found in dogs (101/121, 20/121), cats (45/55, 10/55) and soil (18/21, 3/21) samples, respectively. In addition, several previous studies reported that A. ceylanicum was dominant in dogs [22, 63] and humans from Malaysia [64] and suggested that humans are at risk of zoonotic A. ceylanicum infections from dogs [65].

On the other hand, A. caninum that is known as canine hookworm, was detected not only in stray dogs but also in stray cats, with this being the first such report in Malaysia to date. This finding has demonstrated that there was a cross-infection of A. caninum between cats and dogs in the studied areas and cats were now the victims of dog hookworms, which may be due to the coexistent nature of cats and dogs around communities. Our result were in agreement with previous findings in China [66], Australia [67] and Thailand [68], where A. caninum species were found among cats. Despite A. braziliense being noted among cats in Malaysia [18, 22], none were detected in the current study.

Our results provide important information regarding the helminth parasites present in free-roaming stray animals and environmental soil samples in Klang Valley in the central-west region of Malaysia. All the helminths found in the current study were zoonotic parasites that are potentially capable of infecting human hosts. Additionally, the current study has drawn attention to the fact that A. ceylanicum was the most dominant species of hookworm, not only in stray cats and dogs, but also in the environmental soil of Malaysia. This indicates that stray cats and dogs can be held responsible for zoonotic hookworm infections as well as environmental pollution. Nonetheless, the complementary approached to hookworm control may be achieved by preventative measures, such as preventing cats and dogs from defecating in public areas, cleaning up animal wastes to reduce parasitological contamination in the environment and educating the public to use protective footwear in the parks, playgrounds or beaches.

Supporting Information

S1 Fig. High resolution melting (HRM) curves.

high resolution melting (HRM) curves of 180–200 bp within 5.8S & ITS- 2 amplicon of Ancylostoma species. Aligned fluorescence (normalized fluorescence) was plotted against degree Celsius (°C). The curves included parasites from different sources including stray cats, dogs and from environmental soil.

https://doi.org/10.1371/journal.pone.0142231.s001

(PDF)

Acknowledgments

The authors sincerely thank Dr. Romano Ngui (Department of Parasitology, Faculty of Medicine, University of Malaya (FOMUM), Malaysia) for providing hookworm genomic DNA materials. We thank Dr. Awatif Mohamed Abdulsalam Salih (Department of Parasitology, FOMUM) and Mr. Boon Pin (Department of Molecular Medicine, FOMUM) for their technical assistance in the laboratory. Special thanks also go to the animal shelters’ personnel for their assistance during faecal samples collection.

Author Contributions

Conceived and designed the experiments: ST II NIS RM CKH. Performed the experiments: ST NIS. Analyzed the data: ST NIS II RM LYL. Contributed reagents/materials/analysis tools: ST II CKH LYL. Wrote the paper: ST II RM. Revised the manuscript: LYL

References

  1. 1. Abu-Madi MA, Behnke JM, Prabhaker KS, Al-Ibrahim R, Lewis JW. Intestinal helminths of feral cat populations from urban and suburban districts of Qatar. Veterinary Parasitology. 2010; 168(3–4):284–92. pmid:20031329
  2. 2. Barutzki D, Schaper R. Results of parasitological examinations of faecal samples from cats and dogs in Germany between 2003 and 2010. Parasitology research. 2011; 109(1):45–60.
  3. 3. Beiromvand M, Akhlaghi L, Fattahi Massom SH, Meamar AR, Motevalian A, Oormazdi H, et al. Prevalence of zoonotic intestinal parasites in domestic and stray dogs in a rural area of Iran. Preventive Veterinary Medicine. 2013; 109(1–2):162–7. pmid:23044475
  4. 4. Baker MK, Lange L, Verster A, van der Plaat S. A survey of helminths in domestic cats in the Pretoria area of Transvaal, Republic of South Africa. Part 1: The prevalence and comparison of burdens of helminths in adult and juvenile cats. J S Afr Vet Assoc. 1989; 60(3):139–42. pmid:2634770
  5. 5. Bridger KE, Whitney H. Gastrointestinal parasites in dogs from the Island of St. Pierre off the south coast of Newfoundland. Veterinary parasitology. 2009; 162(1):167–70.
  6. 6. Calvete C, Lucientes J, Castillo JA, Estrada R, Gracia MaJ, Peribáñez MA, et al. Gastrointestinal helminth parasites in stray cats from the mid-Ebro Valley, Spain. Veterinary Parasitology. 1998; 75(2–3):235–40. pmid:9637225
  7. 7. Fisher M. Toxocara cati: an underestimated zoonotic agent. Trends in parasitology. 2003; 19(4):167–70. pmid:12689646
  8. 8. Ngui R, Lee SC, Yap NJ, Tan TK, Aidil RM, Chua KH, et al. Gastrointestinal parasites in rural dogs and cats in Selangor and Pahang states in Peninsular Malaysia. Acta Parasitologica. 2014; 59(4):737–44. pmid:25236287
  9. 9. Palmer CS, Thompson RCA, Traub RJ, Rees R, Robertson ID. National study of the gastrointestinal parasites of dogs and cats in Australia. Veterinary Parasitology. 2008; 151(2–4):181–90. pmid:18055119
  10. 10. Traub RJ. Ancylostoma ceylanicum, a re-emerging but neglected parasitic zoonosis. International Journal for Parasitology. 2013; 43(12–13):1009–15. pmid:23968813
  11. 11. Yoshida Y, Okamoto K, Chiu J-K. Ancylostoma ceylanicum infection in dogs, cats, and man in Taiwan. The American journal of tropical medicine and hygiene. 1968; 17(3):378–81. pmid:5690050
  12. 12. Deplazes P, van Knapen F, Schweiger A, Overgaauw PA. Role of pet dogs and cats in the transmission of helminthic zoonoses in Europe, with a focus on echinococcosis and toxocarosis. Veterinary parasitology. 2011; 182(1):41–53. pmid:21813243
  13. 13. Inpankaew T, Traub R, Thompson R, Sukthana Y. Canine parasitic zoonoses in Bangkok temples. Southeast Asian Journal of Tropical Medicine and Public Health. 2007; 38:247–55. pmid:17539273
  14. 14. Jittapalapong S, Inparnkaew T, Pinyopanuwat N, Kengradomkij C, Sangvaranond A, Wongnakphet S. Gastrointestinal parasites of stray cats in Bangkok Metropolitan areas, Thailand. Katsetsart Journal of Natural Science. 2007; 41:69–73.
  15. 15. Khalafalla RE. A Survey Study on Gastrointestinal Parasites of Stray Cats in Northern Region of Nile Delta, Egypt. Plos One. 2011; 6(7):e20283. pmid:21760884
  16. 16. Labarthe N, Serrão ML, Ferreira AMR, Almeida NKO, Guerrero J. A survey of gastrointestinal helminths in cats of the metropolitan region of Rio de Janeiro, Brazil. Veterinary Parasitology. 2004; 123(1–2):133–9. pmid:15265577
  17. 17. Lefkaditis MA, Pastiu AI, Rodi-Buriel A, Sossidou AV, Panorias AH, Eleftheriadis TG, et al. Helminth burden in stray cats from Thessaloniki, Greece. Helminthologia. 2014; 51(1):73–6.
  18. 18. Mohd Zain SN, Sahimin N, Pal P, Lewis JW. Macroparasite communities in stray cat populations from urban cities in Peninsular Malaysia. Veterinary Parasitology. 2013; 196(3–4):469–77. pmid:23664711
  19. 19. Chan M, Medley G, Jamison D, Bundy D. The evaluation of potential global morbidity attributable to intestinal nematode infections. Parasitology. 1994; 109(03):373–87.
  20. 20. Inpankaew T, Schaer F, Dalsgaard A, Khieu V, Chimnoi W, Chhoun C, et al. High Prevalence of Ancylostoma ceylanicum Hookworm Infections in Humans, Cambodia, 2012. Emerging Infectious Diseases. 2014; 20(6):976–82. pmid:24865815
  21. 21. Khoshoo V, Craver R, Loukas A, Prociv P, Schantz P. Abdominal pain, pan-gut eosinophilia, and dog hookworm infection. Journal of pediatric gastroenterology and nutrition. 1995; 21(4):481. pmid:8583307
  22. 22. Ngui R, Lim YAL, Traub R, Mahmud R, Mistam MS. Epidemiological and Genetic Data Supporting the Transmission of Ancylostoma ceylanicum among Human and Domestic Animals. Plos Neglected Tropical Diseases. 2012; 6(2):e1522. pmid:22347515
  23. 23. Brooker S, Peshu N, Warn PA, Mosobo M, Guyatt HL, Marsh K, et al. The epidemiology of hookworm infection and its contribution to anaemia among pre-school children on the Kenyan coast. Transactions of the Royal Society of Tropical Medicine and Hygiene. 1999; 93(3):240–6. pmid:10492749
  24. 24. Stoltzfus RJ, Chwaya HM, Tielsch JM, Schulze KJ, Albonico M, Savioli L. Epidemiology of iron deficiency anemia in Zanzibari schoolchildren: the importance of hookworms. The American journal of clinical nutrition. 1997; 65(1):153–9. pmid:8988928
  25. 25. Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D, et al. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. The Lancet. 2006; 367(9521):1521–32.
  26. 26. Olsen A, Magnussen P, Ouma JH, Andreassen J, Friis H. The contribution of hookworm and other parasitic infections to haemoglobin and iron status among children and adults in western Kenya. Transactions of the Royal Society of Tropical Medicine and Hygiene. 1998; 92(6):643–9. pmid:10326110
  27. 27. Hsu Y-C, Lin J-T. Intestinal infestation with Ancylostoma ceylanicum. New England Journal of Medicine. 2012; 366(13):e20. pmid:22455438
  28. 28. Bahgat M, El Gindy A, Mahmoud L, Hegab M, Shahin A. Evaluation of the role of Ancylostoma caninum in humans as a cause of acute and recurrent abdominal pain. Journal of the Egyptian Society of Parasitology. 1998; 29(3):873–82.
  29. 29. Costa A, Gomes-Ruiz AC, Rabelo EML. Identification of gender-regulated genes in Ancylostoma braziliense by real-time RT-PCR. Veterinary Parasitology. 2008; 153(3–4):277–84. pmid:18358613
  30. 30. Landmann JK, Prociv P. Experimental human infection with the dog hookworm, Ancylostoma caninum. Medical journal of Australia. 2003; 178(2):69–71. pmid:12526725
  31. 31. Prociv P, Croese J. Human enteric infection with Ancylostoma caninum: hookworms reappraised in the light of a “new” zoonosis. Acta tropica. 1996; 62(1):23–44. pmid:8971276
  32. 32. Bowman DD, Montgomery SP, Zajac AM, Eberhard ML, Kazacos KR. Hookworms of dogs and cats as agents of cutaneous larva migrans. Trends in parasitology. 2010; 26(4):162–7. pmid:20189454
  33. 33. Ritchie LS. An ether sedimentation technique for routine stool examinations. Bulletin of the US Army Medical Department United States Army Medical Department. 1948; 8(4):326.
  34. 34. Hu M, Chilton NB, Zhu X, Gasser RB. Single‐strand conformation polymorphism‐based analysis of mitochondrial cytochrome c oxidase subunit 1 reveals significant substructuring in hookworm populations. Electrophoresis. 2002; 23(1):27–34. pmid:11824618
  35. 35. Gasser RB, Monti JR, Bao-Zhen Q, Polderman AM, Nansen P, Chilton NB. A mutation scanning approach for the identification of hookworm species and analysis of population variation. Molecular and biochemical parasitology. 1998; 92(2):303–12. pmid:9657334
  36. 36. Traub RJ, Robertson ID, Irwin P, Mencke N, Thompson RA. Application of a species-specific PCR-RFLP to identify Ancylostoma eggs directly from canine faeces. Veterinary parasitology. 2004; 123(3):245–55.
  37. 37. Ngui R, Lim YA, Chua KH. Rapid detection and identification of human hookworm infections through high resolution melting (HRM) analysis. PloS one. 2012; 7(7):e41996. pmid:22844538
  38. 38. DOS. Basic population characteristics by administrative districts. Department of Statistics, Kuala Lumpur. 2006. Available: https://www.statistics.gov.my.
    • 39. Waap H, Gomes J, Nunes T. Parasite communities in stray cat populations from Lisbon, Portugal. Journal of Helminthology. 2014; 88(4):389–95. pmid:23719370
    • 40. Traub RJ, Inpankaew T, Sutthikornchai C, Sukthana Y, Thompson RA. PCR-based coprodiagnostic tools reveal dogs as reservoirs of zoonotic ancylostomiasis caused by Ancylostoma ceylanicum in temple communities in Bangkok. Veterinary parasitology. 2008; 155(1):67–73.
    • 41. Traub RJ, Pednekar RP, Cuttell L, Porter RB, Abd Megat Rani PA, Gatne ML. The prevalence and distribution of gastrointestinal parasites of stray and refuge dogs in four locations in India. Veterinary Parasitology. 2014; 205(1–2):233–8. pmid:25139393
    • 42. Lorenzini G, Tasca T, De Carli GA. Prevalence of intestinal parasites in dogs and cats under veterinary care in Porto Alegre, Rio Grande do Sul, Brazil. Brazilian Journal of Veterinary Research and Animal Science. 2007; 44(2):137–45.
    • 43. Ramírez-Barrios RA, Barboza-Mena G, Muñoz J, Angulo-Cubillán F, Hernández E, González F, et al. Prevalence of intestinal parasites in dogs under veterinary care in Maracaibo, Venezuela. Veterinary parasitology. 2004; 121(1):11–20.
    • 44. Scorza AV, Duncan C, Miles L, Lappin MR. Prevalence of selected zoonotic and vector-borne agents in dogs and cats in Costa Rica. Veterinary parasitology. 2011; 183(1):178–83.
    • 45. Krecek R, Moura L, Lucas H, Kelly P. Parasites of stray cats (Felis domesticus L., 1758) on St. Kitts, West Indies. Veterinary parasitology. 2010; 172(1):147–9.
    • 46. Oliveira-Sequeira T, Amarante A, Ferrari T, Nunes L. Prevalence of intestinal parasites in dogs from São Paulo State, Brazil. Veterinary Parasitology. 2002; 103(1):19–27.
    • 47. Engbaek K, Madsen H, Larsen SO. A survey of helminths in stray cats from Copenhagen with ecological aspects. Zeitschrift für Parasitenkunde. 1984; 70(1):87–94. pmid:6538054
    • 48. Hajipour N, Baran AI, Yakhchali M, Khojasteh SMB, Hesari FS, Esmaeilnejad B, et al. A survey study on gastrointestinal parasites of stray cats in Azarshahr, (East Azerbaijan province, Iran). Journal of Parasitic Diseases. 2015:1–6.
    • 49. Yamamoto N, Kon M, Saito T, Maeno N, Koyama M, Sunaoshi K, et al. [Prevalence of intestinal canine and feline parasites in Saitama Prefecture, Japan]. Kansenshogaku zasshi The Journal of the Japanese Association for Infectious Diseases. 2009; 83(3):223–8. pmid:19522305
    • 50. Shalaby H, Abdel-Shafy S, Derbala A. The role of dogs in transmission of Ascaris lumbricoides for humans. Parasitology research. 2010; 106(5):1021–6. pmid:20162430
    • 51. Traub R, Robertson I, Irwin P, Mencke N, Monis P, Thompson R. Humans, dogs and parasitic zoonoses–unravelling the relationships in a remote endemic community in northeast India using molecular tools. Parasitology Research. 2003; 90(3):S156–S7.
    • 52. Zibaei M, Sadjjadi SM, Sarkari B. Prevalence of Toxocara cati and other intestinal helminths in stray cats in Shiraz, Iran. Trop Biomed. 2007; 24(2):39–43. pmid:18209706
    • 53. Lucio-Forster A, Bowman DD. Prevalence of fecal-borne parasites detected by centrifugal flotation in feline samples from two shelters in upstate New York. Journal of feline medicine and surgery. 2011; 13(4):300–3. pmid:21334238
    • 54. Azian M, Sakhone L, Hakim SL, Yusri M, Nurulsyamzawaty Y, Zuhaizam A, et al. Detection of helminth infections in dogs and soil contamination in rural and urban areas. The Southeast Asian journal of tropical medicine and public health. 2008; 39:205–12. pmid:18564703
    • 55. Ghadirian E, Viens P, Strykowski H, Dubreuil F. Epidemiology of toxocariasis in the Montreal area: prevalence of Toxocara and other helminth ova in dogs and soil. Canadian Journal of Public Health/Revue Canadienne de Sante'e Publique. 1976:495–8.
    • 56. Ulukanligil M, Seyrek A, Aslan G, Ozbilge H, Atay S. Environmental pollution with soil-transmitted helminths in Sanliurfa, Turkey. Memorias do Instituto Oswaldo Cruz. 2001; 96(7):903–9. pmid:11685253
    • 57. Martínez-Moreno F, Hernández S, López-Cobos E, Becerra C, Acosta I, Martínez-Moreno A. Estimation of canine intestinal parasites in Cordoba (Spain) and their risk to public health. Veterinary parasitology. 2007; 143(1):7–13. pmid:16971046
    • 58. Giacometti A, Cirioni O, Fortuna M, Osimani P, Antonicelli L, Del Prete M, et al. Environmental and serological evidence for the presence of toxocariasis in the urban area of Ancona, Italy. European journal of epidemiology. 2000; 16(11):1023–6. pmid:11421470
    • 59. Oge S, Oge H. Prevalence of Toxocara spp. eggs in the soil of public parks in Ankara, Turkey. DTW Deutsche tierarztliche Wochenschrift. 2000; 107(2):72–5. pmid:10743338
    • 60. Mizgajska H. Eggs of Toxocara spp. in the environment and their public health implications. Journal of Helminthology. 2001; 75(02):147–51.
    • 61. Gibbons LM, Jacobs DE, Sani RA. Toxocara malaysiensis n. sp.(Nematoda: Ascaridoidea) from the domestic cat (Felis catus Linnaeus, 1758). Journal of Parasitology. 2001; 87(3):660–5. pmid:11426732
    • 62. Li M-W, Zhu X-Q, Gasser RB, Lin R-Q, Sani RA, Lun Z-R, et al. The occurrence of Toxocara malaysiensis in cats in China, confirmed by sequence-based analyses of ribosomal DNA. Parasitology research. 2006; 99(5):554–7. pmid:16636846
    • 63. Choo J, Pang E, Prociv P. Hookworms in dogs of Kuching, Sarawak (North Borneo). Transactions of the Royal Society of Tropical Medicine and Hygiene. 2000; 94(1):21–2. pmid:10748891
    • 64. Ngui R, Ching LS, Kai TT, Roslan MA, Lim YAL. Molecular Identification of Human Hookworm Infections in Economically Disadvantaged Communities in Peninsular Malaysia. American Journal of Tropical Medicine and Hygiene. 2012; 86(5):837–42. pmid:22556084
    • 65. Mahdy MA, Lim YA, Ngui R, Fatimah MS, Choy SH, Yap NJ, et al. Prevalence and zoonotic potential of canine hookworms in Malaysia. Parasites & vectors. 2012; 5(1):1–7.
    • 66. Liu Y, Zheng G, Alsarakibi M, Zhang X, Hu W, Lu P, et al. Molecular identification of Ancylostoma caninum isolated from cats in southern China based on complete ITS sequence. BioMed research international. 2013; 2013.
    • 67. Palmer CS, Traub RJ, Robertson ID, Hobbs RP, Elliot A, While L, et al. The veterinary and public health significance of hookworm in dogs and cats in Australia and the status of A. ceylanicum. Veterinary parasitology. 2007; 145(3):304–13.
    • 68. Setasuban P, Vajrasthira S, Muennoo C. Prevalence and zoonotic potential of Ancylostoma ceylanicum in cats in Thailand. The Southeast Asian journal of tropical medicine and public health. 1976; 7(4):534–9. pmid:1030851