Cryptosporidium parvum and Giardia lamblia recovered from flies on a cattle farm and in a landfill

Evaluating the role of synanthropic filth flies in the transmission of zoonotic parasites: field and laboratory evidence from different animal rearing sites in upper Egypt with focus on Cryptosporidium spp

BACKGROUND

Synanthropic filth flies thrive in human and animal habitats, posing health risks through the transmission of infectious agents. They breed on organic waste, including animal feces, making them carriers of various pathogens. In Egypt, where livestock farming is common and poor sanitation, these flies may contribute to zoonotic disease transmission. The current study investigates parasitic infections in filth flies from three livestock farms in Assiut Governorate, Upper Egypt, highlighting their role as vectors for zoonotic infections, particularly Cryptosporidium, via morphological and molecular tools.

METHODS

A total of 12,749 flies were collected from the study sites via sweep nets. After taxonomic identification, the flies were examined microscopically for parasites using various concentration and staining techniques. Positive samples were further confirmed for infections, particularly for Cryptosporidium parasites, via nested PCR and sequence analysis targeting the COWP and SSU rRNA genes.

RESULTS

This study revealed the presence of several fly species from seven dipteran families, particularly the family Muscidae, primarily Musca domestica, which presented a high parasite infestation rate of 96.6%. This study revealed a high prevalence of various protozoans and helminths in the collected flies. Cryptosporidium was the most prevalent parasite (64.4-100%), infecting all fly species. Entamoeba and Balantidium were also significant, especially in M. domestica (22.6-90.1%, 8.9-100%), Fannia canicularis (10.5-74.4%, 44.2-88.2%), and Borborillus vitripennis (11.1-50%, 37.2-91.4%). Giardia, Trichuris, and Trichostrongylidae had low to moderate prevalence in multiple fly species. Mites are commonly detected on fly exoskeletons, with high infestation rates observed in Musca domestica (77-100%) and Physiphora alceae (66.7-100%). The present study also reported sporadic infections with Trichomonas, Toxocara vitulorum, and pseudoscorpions, along with notable midge larval infestations (52.1%), mainly at site B. Parasitic infections were highest in autumn and spring, with the lowest rates in winter. Molecular identification confirmed the presence of the zoonotic species Cryptosporidium parvum and Cladotanytarsus gedanicus.

CONCLUSION

This study revealed that zoonotic parasites exist in flies and pose potential risks when they are found near humans. Cryptosporidium parvum is the prevalent parasite causing diarrhea outbreaks in animals. This is the first genetic evidence of Cladotanytarsus gedanicus midge from Upper Egypt.

Indicators to complement global monitoring of safely managed on-site sanitation to understand health risks

Halfway through the Sustainable Development Goal (SDG) period, there has been little research on the criteria for monitoring safely managed sanitation under SDG target 6.2. For reporting against SDGs, global indicators are necessarily limited and exclude many safety aspects from a public health perspective. Primary survey data from 31,784 households in seven countries in Asia and Africa were analysed, comparing estimates of safely managed on-site sanitation based on global indicators with five complementary indicators of safety: animal access to excreta, groundwater contamination, overdue emptying, entering containments to empty and inadequate protection during emptying. Application of additional criteria reduced the population with safely managed sanitation by 0.4-35% for specific indicators, with the largest impact due to the risk of groundwater contamination, animal access, and containments overdue for emptying. Combining these indicators across the service chain, excluding transport and treatment, found almost three-quarters of on-site systems currently assessed as safely managed with global indicators were considered unsafe based on complementary indicators. A more comprehensive assessment of safety of on-site sanitation can be achieved through these indicators, which could be integrated into national monitoring systems and used to inform sanitation investments that address local health-related risks.

The global prevalence of parasites in non-biting flies as vectors: a systematic review and meta-analysis

BACKGROUND

Non-biting flies such as the house fly (Musca domestica), the Australian sheep blowfly (Lucilia cuprina) and the oriental latrine fly (Chrysomya megacephala) may carry many parasites. In the present study, we performed a systematic overview of the different species of parasites carried by non-biting flies, as well as of isolation methods, different geographical distribution, seasonality and risk assessment.

METHODS

A meta-analysis was carried out with the aim to review the global prevalence of parasite transmission in non-biting flies. A total sample size of 28,718 non-biting flies reported in studies worldwide satisfied the predetermined selection criteria and was included in the quantitative analysis.

RESULTS

The global prevalence of parasites in non-biting flies was 42.5% (95% confidence interval [CI] 31.9-53.2%; n = 15,888/28,718), with the highest prevalence found for non-biting flies in Africa (58.3%; 95% CI 47.4-69.3%; n = 9144/13,366). A total of 43% (95% CI 32.1-54.4%; n = 7234/15,282) of house flies (M. domestica), the fly species considered to be the most closely associated with humans and animals, were found with parasites. The prevalence of parasites in the intestine of non-biting flies was 37.1% (95% CI 22.7-51.5%; n = 1045/3817), which was significantly higher than the prevalence of parasites isolated from the body surface (35.1%; 95% CI 20.8-49.4%; n = 1199/3649; P < 0.01). Of the 27 reported parasites, a total of 20 known zoonotic parasites were identified, with an infection rate of 38.1% (95% CI 28.2-48.0%; n = 13,572/28,494).

CONCLUSIONS

This study provides a theoretical basis for the public health and ecological significance of parasites transmitted by non-biting flies.

Molecular identification of Cryptosporidium species from domestic ruminants and wild reptiles in Cyprus

The presence of Cryptosporidium species in faecal samples of 32 sheep (Aries bovis), 10 goats (Capra circus), 1 blunt nose viper (Macrovipera lebetina lebetina), 3 Kotschy’s geckos (Mediodactylus kotschyi) and 6 wild stellagamas (Stellagama stellio cypriaca) in Cyprus were investigated by polymerase chain reaction (PCR) and sequencing. Cryptosporidium species were found in 9/32 sheep, 5/10 goats, 2/3 Kotschy’s geckos and 2/6 stellagamas faecal samples based on the sequencing of the 18S rRNA gene. Subtyping was achieved based on the sequencing of the gp60 gene. Four different species have been identified: Cryptosporidium parvum in goats (subtype IIaA15G1R1), C. xiaoi (subtypes XXIIId and XXIIIl) and C. ubiquitum (subtype XIIa) in sheep and C. varanii and C. parvum in lizards; the viper snake sample was negative. This is the first report on the molecular identification of a variety of Cryptosporidium species from domestic ruminants and wild reptiles in the Republic of Cyprus.

A Systematic Review of Zoonotic Enteric Parasites Carried by Flies, Cockroaches, and Dung Beetles

Filth flies, cockroaches, and dung beetles have been close neighbors with humans and animals throughout our joint histories. However, these insects can also serve as vectors for many zoonotic enteric parasites (ZEPs). Zoonoses by ZEPs remain a paramount public health threat due to our close contact with animals, combined with poor water, sanitation, and hygiene access, services, and behaviors in many global regions. Our objective in this systematic review was to determine which ZEPs have been documented in these vectors, to identify risk factors associated with their transmission, and to provide effectual One Health recommendations for curbing their spread. Using PRISMA guidelines, a total of 85 articles published from 1926 to 2021 were reviewed and included in this study. Qualitative analysis revealed that the most common parasites associated with these insects included, but were not limited to: Ascaris spp., Trichuris spp., Entamoeba spp., and Cryptosporidium spp. Additionally, prominent risk factors discovered in the review, such as poor household and community WASH services, unsafe food handling, and exposure to domestic animals and wildlife, significantly increase parasitic transmission and zoonoses. The risk of insect vector transmission in our shared environments makes it critically important to implement a One Health approach in reducing ZEP transmission.

Review on Emerging Waterborne Pathogens in Africa: The Case of Cryptosporidium

Water-related diseases, particularly waterborne diseases, remain significant sources of morbidity and mortality worldwide but especially in developing countries. Emerging waterborne pathogens represent a major health risk. Cryptosporidium is one such pathogen which is globally recognized as a major cause of diarrhea in children and adults. The objective of this paper is not only to review published studies on the impact of these emerging waterborne pathogens but also to identify the various risk factors that favor their transmission. A number of envisaged and needed actions to tackle the challenge of these pathogens in Africa have also been discussed. We have searched the web of ScienceDirect, PubMed, Scopus. ISI Web of Science, SpringerLink, and Google Scholar. The first database search yielded 3099 articles. As a result, 141 studies were submitted for abstract review. A total of 68 articles were selected for full text analysis. After evaluating a considerable number of articles on this topic, the following results were obtained. A number of pathogens are likely to present public health risks, including Cryptosporidium. The contaminating potential of these pathogens is associated with a multitude of factors, such as the effects of climate change, social and behavioral aspects of local populations, water issues, geographical locations that may cause isolation, and inequalities due to lack of transparency of governments in the distribution of financial resources. We stress the need to maintain and strengthen real-time surveillance and rapid epidemiological responses to outbreaks and the emergence of new waterborne pathogens in all countries. African governments, for their part, should be aware of future risks of waterborne protozoan diseases. They must provide immediate and effective responses by establishing technical and financial mechanisms to ensure sufficient quantities of safe drinking water, sewage disposal, and hygiene for all.

Zoonotic enteric parasites in Mongolian people, animals, and the environment: Using One Health to address shared pathogens

BACKGROUND

Cryptosporidium spp. and Giardia duodenalis are important zoonotic enteric pathogens of One Health concern for humans, animals, and the environment. For this study, we investigated parasite prevalence and risk factors among rural, peri-urban, and urban households and environments of Mongolia.

METHODS

This cross-sectional study implemented a household risk factor survey at 250 home sites along with sample collection from humans, animals, flies, and drinking water. Multiplex real-time PCR analysis was conducted to look for Cryptosporidium spp. and/or Giardia duodenalis within household samples.

RESULTS

Lab analysis found one or both zoonotic parasites at 20% of the participating households (51/250). Human samples had a parasite prevalence of 6.4% (27/419), domestic animals at 3.3% (19/570), pooled filth flies at 14.8% (17/115), and drinking water samples at 2% (5/250). Parasite presence at the household was significantly associated with a household's use of an improved drinking water source (OR 0.27; CI 0.12-0.61; p = < 0.01), having an indoor handwashing site (OR 0.41; CI 0.19-0.92; p = 0.03), domestic animal ownership (OR 2.40; CI 1.02-5.65; p = 0.05), and rural location (OR 0.50; CI 0.25-0.98; p = 0.04). Household use of an improved drinking water source remained significant in the multivariate model (OR 0.16; CI 0.04-0.68; p = 0.01).

CONCLUSION

In Mongolia, public and veterinary health are intertwined, particularly for rural herding households. Increased access to safe water, sanitation and hygiene infrastructure could help prevent further transmission of zoonotic enteric parasites. Public health interventions, policy and messaging should utilize a One Health framework employing joint leadership from local human and animal health sectors.

Observation of Giardia sp. in the termite gut of Heterotermes tenuis

Giardia comprises one genus with several morphologically distinct species described in mammals (including humans, marsupials, rodents), birds, and amphibians. This group of protists provokes diarrhoea diseases in humans and animals worldwide. Transmission of the parasite occurs through the faecal-oral route. Regarding the presence of Giardia in invertebrates, some works have shown that flies can transmit Giardia cysts by contact and transport between contaminated faeces and food. In this way, flies would eventually transmit this parasite. To date, Giardia's presence in the gut of other invertebrates has not been described in the literature. Here we show by first time, using scanning electron microscopy, the presence of Giardia-like trophozoites in the gut of termite Heterotermes tenuis. Two groups of Giardia were found based exclusively on the size and the flange shape of the protozoa: one presented eight flagella, a ventral disc, size, and shape very similar to Giardia intestinalis. In contrast, other cells were smaller and showed some differences in the external morphology. We cannot exclude the possibility that they correspond to the same species and that these differences result from protozoan heterogeneity.

Short communication: Screening stable flies and house flies as potential vectors of digital dermatitis in dairy cattle

Digital dermatitis is a bacterial infection that causes lesions above the heel bulbs on cattle hooves, and several bacterial species from the genus Treponema are suspected to be causative agents of this polymicrobial condition. Transmission of the bacteria to healthy cows is understudied, particularly with regard to potential insect vectors. Therefore, the objective of this research was to determine if flies captured from a dairy farm known to have digital dermatitis are contaminated with Treponema bacteria. The DNA-based assays did not detect any Treponema phagedenis from stable flies and house flies collected at a dairy experiencing an outbreak of digital dermatitis. Other potential means of bacterial transmission are discussed.

Prevalence and diversity of gastrointestinal protozoa in Madura cattle at Bangkalan Regency, East Java, Indonesia

Aim:

This study aimed to describe the gastrointestinal protozoa in Madura cattle at Bangkalan Regency, East Java, Indonesia.

Materials and Methods:

A total of 500 samples of Madura cattle feces were collected from 10 districts at Bangkalan Regency. Those ten districts represent the lowland and upland areas, and each district was represented by one village. The collected feces were examined using native, sedimentation, and floating methods. The species identification was determined by their morphology.

Results:

There were 357 (71.4%) samples positively infected with protozoan. The highest rate of sample with protozoan infection was at Kamal District (88.23%), and Bangkalan District (52.83%) was the lowest one. There were six species of protozoa that infected gastrointestinal tract; those are Eimeria spp., Balantidium spp., Isospora spp., Blastocystis spp., Entamoeba spp., and Cryptosporidium spp. The highest number of protozoa found in this research was Eimeria (53.42%) followed by Blastocystis (14.43%). In this study, we found that 295 samples (58.76%) infected by one kind of protozoa, 53 samples (10.56%) infected by two kinds of protozoa, and 11 samples (2.19%) infected by three kinds of protozoa. In addition, there were 65.54% of bulls infected with protozoa, considerably lower than cows (72.97%). Cattle aged 6 months-2 years old (73.39%) and >2 years old (71.25%) are known more prone to protozoan infections than cattle aged <6 months (66.15%).

Conclusion:

The present study revealed that protozoan infection of cattle is common in Bangkalan Regency. Studies focused on determining that the prevalence of protozoan, risk factors for the parasitism, and the geographic distribution are needed and will be effective guide for prevention and control measures.

The Potential Role of Synanthropic Rodents and Flies in the Transmission of Enterocytozoon bieneusi on a Dairy Cattle farm in China

Enterocytozoon bieneusi causes microsporidiosis, a condition with complex epidemiology involving both direct and indirect transmission routes. To assess the potential role of synanthropic rodents and flies in the transmission of this pathogen, a total of 277 cattle fecal samples, 199 synanthropic rodents, and 50 batches of 20 flies were collected from a cattle farm. These samples were screened for the presence of E. bieneusi by PCR and sequencing of the internal transcribed spacer (ITS) region of the rRNA gene. The positive rates of cattle, synanthropic rodents, and flies were 11.9% (33/277), 4.0% (8/199) and 12.0% (6/50), respectively. Nineteen genotypes were identified, including 11 known genotypes (BEB6, I, COS-I, EbpC, D, J, CHS5, CHG1 to CHG3 and CHG14) and eight novel genotypes (named CHC9 to CHC16). The dominant genotype detected in the present study, BEB6, was found in all three categories of hosts. Moreover, human pathogenic genotypes D and EbpC were also observed in both synanthropic rodents and flies. These results demonstrate that synanthropic rodents and flies may act as biological disseminator or mechanical vector in the transmission of microsporidiosis to humans. Efforts should be made to minimize threats from these commensal animals to public health.

Multilocus genotyping of Giardia duodenalis infecting rabbits in Ogun State, Nigeria

Giardiasis is a cosmopolitan gastrointestinal protozoal parasite that infects humans and various animals worldwide. To assess the zoonotic transmission potential of Giardia, molecular characterization is required. We are unaware of any report on the genotypes of Giardia infecting rabbits in Nigeria. Molecular detection and genotyping of Giardia duodenalis were conducted in a herd of adult Chinchilla rabbits (Oryctolagus cuniculus) managed on the Teaching and Research farm of the Federal University of Agriculture, Abeokuta located in a southwestern state of Nigeria by analysis of the small-subunit ribosomal RNA (ssu rRNA), glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi) and beta-giardin (bg) genes. An overall prevalence of 72.3% (60/83) was recorded in the rabbits with no statistically significant (p > .05) influence of sex on the distribution of the infection in the herd. All the 19 isolates amplified at the four genetic loci were identified as G. duodenalis assemblage BIV by multiple alignment analysis of their consensus sequences. Novel nucleotide substitutions were identified in two isolates at the ssu rRNA locus. Phylogenetic analysis revealed that all ssu rRNA genotypes were closely related to G. duodenalis assemblage B of cattle and human origin. Findings of this study suggest that the rabbits harbour potentially zoonotic assemblage BIV that portends a high risk to students and staff of the University who are in regular contact with the animals.

Cryptosporidium and Giardia in Africa: current and future challenges

Cryptosporidium and Giardia are important causes of diarrhoeal illness. Adequate knowledge of the molecular diversity and geographical distribution of these parasites and the environmental and climatic variables that influence their prevalence is important for effective control of infection in at-risk populations, yet relatively little is known about the epidemiology of these parasites in Africa. Cryptosporidium is associated with moderate to severe diarrhoea and increased mortality in African countries and both parasites negatively affect child growth and development. Malnutrition and HIV status are also important contributors to the prevalence of Cryptosporidium and Giardia in African countries. Molecular typing of both parasites in humans, domestic animals and wildlife to date indicates a complex picture of both anthroponotic, zoonotic and spill-back transmission cycles that requires further investigation. For Cryptosporidium, the only available drug (nitazoxanide) is ineffective in HIV and malnourished individuals and therefore more effective drugs are a high priority. Several classes of drugs with good efficacy exist for Giardia, but dosing regimens are suboptimal and emerging resistance threatens clinical utility. Climate change and population growth are also predicted to increase both malnutrition and the prevalence of these parasites in water sources. Dedicated and co-ordinated commitments from African governments involving "One Health" initiatives with multidisciplinary teams of veterinarians, medical workers, relevant government authorities, and public health specialists working together are essential to control and prevent the burden of disease caused by these parasites.

Prevalence of Cryptosporidium oocysts and Giardia cysts in raw and treated sewage sludges

Treated sludge from wastewater treatment plants (WWTPs) is commonly used in agriculture as fertilizers and to amend soils. The most significant health hazard for sewage sludge relates to the wide range of pathogenic microorganisms such as protozoa parasites.The objective of this study was to collect quantitative data on Cryptosporidium oocysts and Giardia cysts in the treated sludge in wastewater treatment facilities in Spain. Sludge from five WWTPs with different stabilization processes has been analysed for the presence of Cryptosporidium and Giardia in the raw sludge and after the sludge treatment. A composting plant (CP) has also been assessed. After a sedimentation step, sludge samples were processed and (oo)cysts were isolated by immunomagnetic separation (IMS) and detected by immunofluorescence assay (IFA). Results obtained in this study showed that Cryptosporidium oocysts and Giardia cysts were present in 26 of the 30 samples (86.6%) of raw sludge samples. In treated sludge samples, (oo)cysts have been observed in all WWTP's analysed (25 samples) with different stabilization treatment (83.3%). Only in samples from the CP no (oo)cysts were detected. This study provides evidence that (oo)cysts are present in sewage sludge-end products from wastewater treatment processes with the negative consequences for public health.

Environmental Factors Associated with High Fly Densities and Diarrhea in Vellore, India

Diarrhea causes significant morbidity and mortality in Indian children under 5 years of age. Flies carry enteric pathogens and may mediate foodborne infections. In this study, we characterized fly densities as a determinant of infectious diarrhea in a longitudinal cohort of 160 urban and 80 rural households with 1,274 individuals (27% under 5 years of age) in Vellore, India. Household questionnaires on living conditions were completed at enrollment. Fly abundance was measured during the wet and dry seasons using fly ribbons placed in kitchens. PCRs for enteric bacteria, viruses, and protozoa were performed on 60 fly samples. Forty-three (72%) fly samples were positive for the following pathogens: norovirus (50%), Salmonella spp. (46.7%), rotavirus (6.7%), and Escherichia coli (6.7%). Ninety-one episodes of diarrhea occurred (89% in children under 5 years of age). Stool pathogens isolated in 24 of 77 (31%) samples included E. coli, Shigella spp., Vibrio spp., Giardia, Cryptosporidium, and rotavirus. Multivariate log-linear models were used to explore the relationships between diarrhea and fly densities, controlling for demographics, hygiene, and human-animal interactions. Fly abundance was 6 times higher in rural than urban sites (P < 0.0001). Disposal of garbage close to homes and rural living were significant risk factors for high fly densities. The presence of latrines was protective against high fly densities and diarrhea. The adjusted relative risks of diarrheal episodes and duration of diarrhea, associated with fly density at the 75th percentile, were 1.18 (95% confidence interval [CI], 1.03 to 1.34) and 1.15 (95% CI, 1.02 to 1.29), respectively. Flies harbored enteric pathogens, including norovirus, a poorly documented pathogen on flies.

Genotyping and subtyping Cryptosporidium parvum and Giardia duodenalis carried by flies on dairy farms in Henan, China

Background

Cryptosporidium and Giardia are important causes of diarrhea diseases in humans and animals worldwide, and both of them are transmitted by the fecal–oral route, either by direct contact or by the ingestion of contaminated food or water. The role of flies in the mechanical transmission of Cryptosporidium and Giardia has been receiving increasing attention. To date, no information is available in China about the occurrence of Cryptosporidium and Giardia in flies. We here investigated Cryptosporidium and Giardia in flies on dairy farms in Henan Province, China, at the genotype and subtype levels.

Methods

Eight hundred flies were randomly collected from two dairy farms from July 2010 to September 2010 and were divided evenly into 40 batches. The fly samples were screened for the presence of Cryptosporidium and Giardia with nested PCR. Cryptosporidium was genotyped and subtyped by analyzing the DNA sequences of small subunit rRNA (SSU rRNA) and 60-kDa glycoprotein (gp60) genes, respectively. The identity of Giardia was determined by sequence analyzing of the triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh), and β-giardin (bg) genes.

Results

Forty batches of flies had 10% of contamination with Cryptosporidium or Giardia, with a mixed infection of the two parasites in one batch of flies. The Cryptosporidium isolates were identified as C. parvum at the SSU rRNA locus, and all belonged to subtype IIdA19G1 at the gp60 locus. The Giardia isolates were all identified as assemblage E of G. duodenalis at the tpi, gdh, and bg loci. One novel subtype of assemblage E was identified based on the gdh and bg loci.

Conclusions

This is the first molecular study of Cryptosporidium and Giardia in flies identified at both genotype and subtype levels. SSU rRNA and gp60 sequences of C. parvum in flies was 100% homologous with those derived from humans, suggesting flies act as an epidemiological vector of zoonotic cryptosporidiosis. The variable PCR efficiencies observed in the analysis of Giardia at different loci suggest that we should use the multilocus genotyping tool in future studies to increase the detection rate, and importantly, to obtain more complete genetic information on Giardia isolates.

Human intestinal parasites in non-biting synanthropic flies in Ogun State, Nigeria

Filth-feeding and breeding, non-biting synanthropic flies have been incriminated in the dissemination of human enteropathogens in the environment. This study determined the species of non-biting synanthropic flies associated with four filthy sites in Ilishan, Ogun State, southwest Nigeria, and assessed their potentials for mechanical transmission of human intestinal parasites. 7190 flies identified as Musca domestica (33.94%), Chrysomya megacephala (26.01%), Musca sorbens (23.23%), Lucilia cuprina (8.76%), Calliphora vicina (4.59%), Sarcophaga sp. (2.78%) and Fannia scalaris (0.70%) were examined for human intestinal parasites by the formol-ether concentration and modified Ziehl-Neelsen techniques. Eggs of the following parasites: Ascaris lumbricoides (34.08%), Trichuris trichiura (25.87%), hookworms (20.45%), Taenia sp. (2.36%), Hymenolepis nana (1.11%), Enterobius vermicularis (0.56%), Strongyloides stercoralis (larvae; 3.89%) and cysts of Entamoeba histolytica/dispar (27.26%), Entamoeba coli (22.67%), Giardia lamblia (3.34%) and Cryptosporidium sp. (1.81%) were isolated from the body surfaces and or gut contents of 75.24% of 719 pooled fly batches. The helminths A. lumbricoides and T. trichiura and the protozoans, E. histolytica/dispar and E. coli were the dominant parasites detected, both on body surfaces and in the gut contents of flies. C. megacephala was the highest carrier of parasites (diversity and number). More parasites were isolated from the gut than from body surfaces (P < 0.05). Flies from soiled ground often carried more parasites than those from abattoir, garbage or open-air market. Synanthropic fly species identified in this study can be of potential epidemiological importance as mechanical transmitters of human intestinal parasites acquired naturally from filth and carried on their body surfaces and or in the gut, because of their vagility and feeding mechanisms.

Giardia--from genome to proteome

In this review, the current status of genomic and proteomic research on Giardia is examined in terms of evolutionary biology, phylogenetic relationships and taxonomy. The review also describes how characterising genetic variation in Giardia from numerous hosts and endemic areas has provided a better understanding of life cycle patterns, transmission and the epidemiology of Giardia infections in humans, domestic animals and wildlife. Some progress has been made in relating genomic information to the phenotype of Giardia, and as a consequence, new information has been obtained on aspects of developmental biology and the host-parasite relationship. However, deficiencies remain in our understanding of pathogenesis and host specificity, highlighting the limitations of currently available genomic datasets.

Epidemiology of enteric disease in C-EnterNet's pilot site - Waterloo region, Ontario, 1990 to 2004

OBJECTIVE

The objective of the present study was to describe the epidemiology of reportable enteric illness in Ontario's Waterloo region, including comparing calculated incidence rates with published rates, and adjusting for under-reporting to determine the number of community cases, where published data were available.

METHODS

Descriptive analyses were performed on reportable disease data for 13 enteric diseases collected in the Waterloo region from 1990 to 2004. Poisson and negative binomial regression analyses were used to investigate differences in incidence rates among age, sex, the 15 years of data and seasons. Disease-specific incidence rates were calculated and compared with the literature, where possible. Under-reporting ratios from the literature were applied to estimate the number of cases of campylobacteriosis, nontyphoidal salmonellosis and verotoxigenic Escherichia coli infection at the community level.

RESULTS

Over the study period, the average annual age- and sex-adjusted incidence rates per 100,000 population were highest for campylobacteriosis (49.69 cases), followed by giardiasis (31.87 cases) and nontyphoidal salmonellosis (25.97 cases). The incidence of most enteric illnesses peaked in the summer. The highest incidence occurred in young children, followed by adults in their 20s. Diarrhea (85.4%) was the most frequently reported symptom, food (57.4%) was the most commonly reported probable source, and home (41.7%) and travel (37.0%) were the two most frequently reported risk settings.

CONCLUSIONS

Enteric illness was a significant health burden in the Waterloo region from 1990 to 2004. Because reportable disease data are subject to under-reporting, it is likely that the true burden is greater than estimated in the present study.

Zoonotic enteric protozoa

A growing number of enteric protozoan species are considered to have zoonotic potential. Their clinical impact varies and in many cases is poorly defined. Similarly, the epidemiology of infections, particularly the role of non-human hosts, requires further study. In this review, new information on the life cycles and transmission of Giardia, Cryptosporidium, Entamoeba, Blastocystis and Balantidium are examined in the context of zoonotic potential, as well as polyparasitism and clinical significance.

Cryptosporidium recovered from Musca domestica, Musca sorbens and mango juice accessed by synanthropic flies in Bahirdar, Ethiopia

The study was conducted to determine the role of house flies, Musca domestica and Musca sorbens to carry Cryptosporidium species in natural environment and filth flies potential for contamination of food item they visited using acid-fast stain technique. Cryptosporidium was identified from flies collected in dairy cow barns, butchery, market and defecating grounds. Musca domestica captured from dairy cow barns and M. sorbens from defecating ground were found carrying more oocyst of Cryptosporidium parvum. Oocyst load per fly for M. domestica and M. sorbens was 5.84 and 3.42, respectively. Flies' population dynamics in each month had little relation to the monthly oocyst frequency, r = 0.06 and 0.02 for M. domestica and M. sorbens, respectively. Cryptosporidium species oocysts were isolated from frozen mango juice, which filth flies visited in dairy farm barn. Load of oocysts in the mango juice was dependent on time contact of flies with mango juice and more oocysts were recovered (P < 0.05) in mango juice samples accessed by filth flies for longer period. Role of filth flies to carry and deposit Cryptosporidium species oocyst for development of food-borne cryptosporidiosis is signified.

Update on Cyclospora cayetanensis, a food-borne and waterborne parasite

The coccidian parasite Cyclospora cayetanensis is recognized as an emerging pathogen that causes protracted diarrhea in humans. The first cases of Cyclospora infection were reported in the late 1970s and were observed among expatriates and travelers in regions where infections are endemic. Since then, Cyclospora has been considered a cause of traveler's diarrhea. Epidemiological investigations were reported and examined in areas of endemicity even before the true identity of Cyclospora was elucidated. Cyclospora was fully characterized in the early 1990s, but it was not until the 1995 Cyclospora outbreak in the United States and Canada that it caught the attention of the public and physicians. The biology, clinical presentation, epidemiology, diagnosis, treatment, and control of cyclosporiasis are reviewed, with a focus on diagnostic assays currently being used for clinical and environmental samples. Challenges and limitations in working with Cyclospora are also discussed.

Multiple-subgenotype infections of Giardia intestinalis detected in Palestinian clinical cases using a subcloning approach

To evaluate the geographic distribution of Giardia intestinalis genotypes in Nablus, West Bank, Palestine, a genotyping study was performed using clinical fecal samples. Microscopic examination confirmed that 8 of 69 (11.6%) samples were G. intestinalis positive, and subsequent genotyping analyses targeting the small-subunit ribosomal RNA (18S rRNA) and glutamate dehydrogenase (GDH) genes revealed the G. intestinalis genotypes within the 8 samples. Of these 8 samples, 6 were clustered with assemblage A-II and the remaining 2 samples were clustered with assemblage B by 18S rRNA gene analysis; however, direct sequencing of the GDH gene segments from the latter 2 samples showed a mixed infection profile. To assess those samples, we employed a subcloning approach and successfully isolated 6 independent assemblage B subgenotypes. These partial GDH gene sequences (393 bp) had 15 single-nucleotide polymorphisms, all of which were synonymous transition substitutions at the third nucleotide position of codons. From the results, we concluded that the highly polymorphic gene loci such as GDH gene locus might provide us an opportunity to obtain a detailed molecular data even from the samples with multiple-subgenotype mixed infections. Therefore, subcloning approach is recommended in genotyping studies, especially in those conducted in giardiasis-endemic areas, where the repeated and cumulative infections could be commonly expected.

A longitudinal study of Giardia duodenalis genotypes in dairy cows from birth to 2 years of age

Fecal specimens were collected from 30 calves from birth to 24 months of age at a dairy farm in Maryland to determine the prevalence of Giardia duodenalis genotypes in cattle of different ages. Fecal samples were subjected to density gradient centrifugation to remove debris and concentrate cysts. Specimens were analyzed by immunofluorescence microscopy and polymerase chain reaction (PCR). All PCR positive specimens were sequenced using the SSU-rRNA gene of Giardia. All 30 calves shed G. duodenalis cysts at some time during the study. Of 990 specimens, 312 were positive for G. duodenalis (31.5%). The highest prevalence of infection occurred at weeks 4 and 5 of age with 25 out of 30 calves shedding cysts at those sampling times. Overall, pre-weaned calves (<8 weeks of age) exhibited the highest prevalence (60.8%), followed by post-weaned calves (3-12 months of age) (32.1%) and heifers (12-24 months of age) (11.4%). Sequence analysis of the 312 PCR-positive samples revealed the presence of both Assemblages A and E, G. duodenalis, with cumulative prevalences of 70% and 100%, respectively. Assemblage A was not detected in pre-weaned calves, but was detected in 6.9% and 4.7% of post-weaned calves and heifers, respectively. These data indicate not only that calves are infected with both Assemblages A and E simultaneously, but also that infections with zoonotic Assemblage A, G. duodenalis are more common than previously reported. Thus, calves appear to be a more significant reservoir of human infectious G. duodenalis than previous data have suggested.

Paradoxical helminthiasis and giardiasis in Cape Town, South Africa: epidemiology and control

BACKGROUND

South Africa has endorsed a World Health Assembly (WHA) resolution calling for control of soil-transmitted helminths (STHs). In Cape Town, services and housing that exist in old-established suburbs should minimise the prevalence of intestinal parasitic infections, even when residents are poor. Where families live in shacks in densely-populated areas without effective sanitation, more than 90% of children can be infected by STHs. The humoral immune response to worms theoretically favours infection by Mycobacterium tuberculosis and HIV.

OBJECTIVES

Obtain estimates of gender-, age-, school-related and overall prevalence of helminthiasis and giardiasis in a low-income but well-serviced community. Assess possible sources of infection. Alert health services to the need for control measures and the threat from protozoal pathogens. Warn that the immune response to intestinal parasites may favour tuberculosis (TB) and HIV/AIDS.

METHODS

A cross-sectional study of the prevalence of helminthiasis and giardiasis was carried out in a large, non-selective sample of children attending nine schools. Gender, school and age effects were related to non-medical preventive services, sewage disposal practices and possible sources of infection.

RESULTS

The overall STH infestation rate was 55.8%. Prevalence was inluenced by school and age but not by gender. Eggs and cysts were seen at the following prevalence: Ascaris 24.8%; Trichuris 50.6%; Hymenolepis nana 2.2%; Enterobius 0.6%; Giardia 17.3%; hookworm 0.08%; and Trichostrongylus 0.1%. Approximately 60% of sewage sludge is used in a form that will contain viable eggs and cysts.

CONCLUSION

Prevalence trends in this old community in Cape Town could indicate infection by swallowing eggs or cysts on food or in water, more than by exposure to polluted soil. Sewage sludge and effluent might be sources of infection. In adjacent, under serviced, newer communities, promiscuous defecation occurs. Probable vectors are discussed. The immune response to intestinal parasites might be a risk factor for HIV/AIDS and TB.

Between-year variation and spatial dynamics of Cryptosporidium spp. and Giardia spp. infections in naturally infected rodent populations

Prevalence and abundance of Cryptosporidium spp. and Giardia spp. infections were studied over the 8-year period in 3 species of rodents in N.E. Poland (bank vole Myodes glareolus-1523; yellow-necked mouse Apodemus flavicollis- 638; common vole Microtus arvalis- 419). Prevalence was 53.8, 28.1 and 62.3% respectively for Cryptosporidium spp. and 58.3, 24.4 and 74.2% respectively for Giardia spp. Prevalence and abundance of infection varied markedly across 8 years of the study with 1998 and 2002 being years of higher prevalence and abundance, following changes in the densities of host species. The distribution of intestinal protozoa in forest rodents did not vary in the 3 isolated sites during the 4-year study. In the case of Cryptosporidium, fewer older animals carried infection and infections of the oldest bank and common voles were relatively milder. In the case of Giardia in yellow-necked mice, infections were more common in older age classes (2 and 3). The two species showed significant co-occurrence and in animals carrying both species there was a strong significant positive correlation between abundance of infection with each. These data are discussed in relation to the parasite genotypes identified in this region and in respect of the role of various ecological factors in shaping of intestinal protozoa communities.

Synanthropic flies as vectors of Cryptosporidium and Giardia among livestock and wildlife in a multispecies agricultural complex

The capacity of synanthropic flies belonging to the families Calliphoridae, Sarcophagidae, and Muscidae to serve as mechanical vectors of Cryptosporidium and Giardia among livestock and wildlife in a multispecies agricultural complex in northwest Georgia (USA) was studied using fluorescent in situ hybridization (FISH) and immunofluorescent antibody (IFA) techniques. Flies from all three families were carrying viable Cryptosporidium oocysts and Giardia cysts internally and externally, and deposited them on trap surfaces. Furthermore, the contaminated flies and trap surfaces occurred in association with each of the four domestic animal units (beef, dairy, equine, and sheep), and in wildlife areas dominated by deer (Odocoileus virginianus) and Canada Geese (Branta canadensis). Cryptosporidium was isolated from 55.56% of the fly samples, whereas Giardia was isolated from only 7.94%. The highest numbers of Cryptosporidium were associated with cattle and wildlife areas, while Giardia occurred in greatest numbers in the sheep area. Cryptosporidium was isolated comparably from exoskeletal elutants and fly homogenates, but Giardia was isolated primarily from homogenates, indicating primarily internal transport in the latter. Surfaces visited by the flies (i.e., traps) became contaminated by both Cryptosporidium (18.89%) and Giardia (1.11%). In conclusion, these flies can serve as mechanical vectors of both Cryptosporidium and Giardia in all of these settings, and undoubtedly play a role in movement of these pathogens among the various host species.

Sheep management and cryptosporidiosis in central Mexico

To establish the association between sheep farm management practices and cryptosporidiosis in Central Mexico, 37 farms were invited and questionnaires answered by owners. Faeces samples were taken from lambs under 3 months old and ewes in the farms. Parasites were identified by modified Ziehl-Neelsen stain. Questionnaire included: general farm information, facilities characteristics, facilities cleaning measures, water use and farm and animal management practices. Farms were grouped in a low ( Pound 3,37%), medium (3.38-49.9%) and high basis ((3)50%) according to prevalence. Associations (OR) were calculated according to positivity, compared by chi-square test. A general prevalence of 34,33% was found. Five variables showed statistical significance (p<0.05). Associations found were: use of bed, grazing place, and bottle cleaning. The only association found between management practices and cryptosporidiosis that could represent a risk was the grazing place. This report is the first one in the country regarding predisposing conditions for cryptosporidiosis.

Occurrence of Cryptosporidium and Giardia in sewage sludge and solid waste landfill leachate and quantitative comparative analysis of sanitization treatments on pathogen inactivation

Circulation of Cryptosporidum and Giardia in the environment can be facilitated by spreading of sewage sludge on agricultural or livestock grazing lands or depositing in landfills. Solid waste landfill leachate and sewage sludge samples were quantitatively tested for C. parvum and C. hominis oocysts, and G. lamblia cysts by the combined multiplexed fluorescence in situ hybridization (FISH) and immunofluorescent antibody (IFA) method. Subsequently, the effects of four sanitization treatments (i.e., ultrasound and microwave energy disintegrations, and quicklime and top-soil stabilization) on inactivation of these pathogens were determined. The landfill leachate samples were positive for Giardia, and sewage sludge samples for both Cryptosporididium and Giardia. The overall concentration of G. lamblia cysts (mean; 24.2/g) was significantly higher (P<0.01) than the concentration of C. parvum and C. hominis oocysts (mean; 14.0/g). Sonication reduced the load of G. lamblia cysts to non-detectable levels in 12 of 21 samples (57.1%), and in 5 of 6 samples (83.3%) for C. parvum and C. hominis. Quicklime stabilization treatment was 100% effective in inactivation of Cryptosporidium and Giardia, and microwave energy disintegration lacked the efficacy. Top-soil stabilization treatment reduced gradually the load of both pathogens which was consistent with the serial dilution of sewage sludge with the soil substrate. This study demonstrated that sewage sludge and landfill leachate contained high numbers of potentially viable, human-virulent species of Cryptosporidium and Giardia, and that sonication and quicklime stabilization were the most effective treatments for sanitization of sewage sludge and solid waste landfill leachates.

Human-virulent microsporidian spores in solid waste landfill leachate and sewage sludge, and effects of sanitization treatments on their inactivation

Solid waste landfill leachate and sewage sludge samples were quantitatively tested for viable Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, and Encephalitozoon cuniculi spores by the multiplexed fluorescence in situ hybridization (FISH) assay. The landfill leachate samples tested positive for E. bieneusi and the sludge samples for E. bieneusi and E. intestinalis. The effects of four sanitization treatments on the inactivation of these pathogens were assessed. Depending on the variations utilized in the ultrasound disintegration, sonication reduced the load of human-virulent microsporidian spores to nondetectable levels in 19 out of 27 samples (70.4%). Quicklime stabilization was 100% effective, whereas microwave energy disintegration was 100% ineffective against the spores of E. bieneusi and E. intestinalis. Top-soil stabilization treatment gradually reduced the load of both pathogens, consistent with the serial dilution of sewage sludge with the soil substrate. This study demonstrated that sewage sludge and landfill leachate contained high numbers of viable, human-virulent microsporidian spores, and that sonication and quicklime stabilization were the most effective treatments for the sanitization of sewage sludge and solid waste landfill leachates. Multiplexed FISH assay is a reliable quantitative molecular fluorescence microscopy method for the simultaneous identification of E. bieneusi, E. intestinalis, E. hellem, and E. cuniculi spores in environmental samples.

Human enteropathogen load in activated sewage sludge and corresponding sewage sludge end products

This study demonstrated a significant reduction in the concentrations of Cryptosporidium parvum and Cryptosporidium hominis oocysts, Giardia lamblia cysts, and spores of human-virulent microsporidia in dewatered and biologically stabilized sewage sludge cake end products compared to those of the respective pathogens in the corresponding samples collected during the sludge activation process.

Critical processes affecting Cryptosporidium oocyst survival in the environment

Cryptosporidium are parasitic protozoans that cause gastrointestinal disease and represent a significant risk to public health. Cryptosporidium oocysts are prevalent in surface waters as a result of human, livestock and native animal faecal contamination. The resistance of oocysts to the concentrations of chlorine and monochloramine used to disinfect potable water increases the risk of waterborne transmission via drinking water. In addition to being resistant to commonly used disinfectants, it is thought that oocysts can persist in the environment and be readily mobilized by precipitation events. This paper will review the critical processes involved in the inactivation or removal of oocysts in the terrestrial and aquatic environments and consider how these processes will respond in the context of climate change.

Paradoxical helminthiasis and giardiasis in Cape Town, South Africa: epidemiology and control

BACKGROUND

South Africa has endorsed a World Health Assembly (WHA) resolution calling for control of soil-transmitted helminths (STHs). In Cape Town, services and housing that exist in old-established suburbs should minimise the prevalence of intestinal parasitic infections, even when residents are poor. Where families live in shacks in densely-populated areas without effective sanitation, more than 90% of children can be infected by STHs. The humoral immune response to worms theoretically favours infection by Mycobacterium tuberculosis and HIV.

OBJECTIVES

Obtain estimates of gender-, age-, school-related and overall prevalence of helminthiasis and giardiasis in a low-income but well-serviced community. Assess possible sources of infection. Alert health services to the need for control measures and the threat from protozoal pathogens. Warn that the immune response to intestinal parasites may favour tuberculosis (TB) and HIV/AIDS.

METHODS

A cross-sectional study of the prevalence of helminthiasis and giardiasis was carried out in a large, non-selective sample of children attending nine schools. Gender, school and age effects were related to non-medical preventive services, sewage disposal practices and possible sources of infection.

RESULTS

The overall STH infestation rate was 55.8%. Prevalence was influenced by school and age but not by gender. Eggs and cysts were seen at the following prevalences: Ascaris 24.8%; Trichuris 50.6%; Hymenolepis nana 2.2%; Enterobius 0.6%; Giardia 17.3%; hookworm 0.08%; and Trichostrongylus 0.1%. Approximately 60% of sewage sludge is used in a form that will contain viable eggs and cysts.

CONCLUSIONS

Prevalence trends in this old community in Cape Town could indicate infection by swallowing eggs or cysts on food or in water, more than by exposure to polluted soil. Sewage sludge and effluent might be sources of infection. In adjacent, under-serviced, newer communities, promiscuous defaecation occurs. Probable vectors are discussed. The immune response to intestinal parasites might be a risk factor for HIV/AIDS and TB.

Mechanical transmission of human protozoan parasites by insects

The filthy breeding habits, feeding mechanisms, and indiscriminate travel between filth and food make some groups of synanthropic insects such as nonbiting flies and cockroaches efficient vectors of human enteric protozoan parasites. Twenty-one species of filth flies have been listed by regulatory agencies concerned with sanitation and public health as causative agents of gastrointestinal diseases based on synanthropy, endophily, communicative behavior, and strong attraction to filth and human food. Outbreaks and cases of food-borne diarrheal diseases in urban and rural areas are closely related to the seasonal increase in abundance of filth flies, and enforced fly control is closely related to reductions in the occurrence of such diseases. Mechanical transmission of human parasites by nonbiting flies and epidemiological involvement of other synanthropic insects in human food-borne diseases have not received adequate scientific attention.