Possible transmission of Strongyloides fuelleborni between working Southern pig-tailed macaques (Macaca nemestrina) and their owners in Southern Thailand: Molecular identification and diversity

Human strongyloidiasis is caused by Strongyloides stercoralis, S. fuelleborni fuelleborni and Strongyloides f. kellyi. Strongyloides fuelleborni is a soil-transmitted nematode parasite typically infecting non-human primates. The southern pig-tailed macaque (Macaca nemestrina) is distributed throughout the southern part of Thailand and could be a source of zoonotic transmission of this nematode. Here, we extracted DNA from Strongyloides speciescultured from the feces of southern pig-tailed macaques and their owners. Using PCR and sequencing of the extracted DNA, we compared the nucleotide sequences of these worms using portions of the 18S rDNA hypervariable region IV (HVR-IV) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. Sequences from the 18S rRNA gene were obtained from worms from 23 southern pig-tailed macaques and from one owner. These sequences were identical with each other and with all East and Southeast Asian S. fuelleborni sequences (from Japan, Thailand, and Lao PDR) in the GenBank database. A median-joining network of published cox1 sequences (n = 123), in combination with the present 24 new sequences, represented 107 haplotypes distributed among six clusters, which corresponded to geographical localities but did not relate to host species. The S. fuelleborni cox1 sequences from some southern pig-tailed macaques and the one infected owner shared the same cox1 haplotype. This is the first evidence of likely zoonotic transmission of S. fuelleborni from a reservoir host, M. nemestrina.

The Strongyloides stercoralis-hookworms association as a path to the estimation of the global burden of strongyloidiasis: A systematic review

TRIAL REGISTRATION

PROSPERO (registration code CRD42019131127).

Detection of classic and cryptic Strongyloides genotypes by deep amplicon sequencing: A preliminary survey of dog and human specimens collected from remote Australian communities

Strongyloidiasis is caused by the human infective nematodes Strongyloides stercoralis, Strongyloides fuelleborni subsp. fuelleborni and Strongyloides fuelleborni subsp. kellyi. The zoonotic potential of S. stercoralis and the potential role of dogs in the maintenance of strongyloidiasis transmission has been a topic of interest and discussion for many years. In Australia, strongyloidiasis is prevalent in remote socioeconomically disadvantaged communities in the north of the continent. Being an isolated continent that has been separated from other regions for a long geological period, description of diversity of Australian Strongyloides genotypes adds to our understanding of the genetic diversity within the genus. Using PCR and amplicon sequencing (Illumina sequencing technology), we sequenced the Strongyloides SSU rDNA hyper-variable I and hyper-variable IV regions using Strongyloides-specific primers, and a fragment of the mtDNA cox1 gene using primers that are broadly specific for Strongyloides sp. and hookworms. These loci were amplified from DNA extracted from Australian human and dog faeces, and one human sputum sample. Using this approach, we confirm for the first time that potentially zoonotic S. stercoralis populations are present in Australia, suggesting that dogs represent a potential reservoir of human strongyloidiasis in remote Australian communities.

MaxEnt modeling of soil-transmitted helminth infection distributions in Thailand

Infections due to soil-transmitted helminths (STHs), i.e. Ascaris lumbricoides, Trichuris trichiura, hookworms, and Strongyloides stercoralis, are widely distributed in tropical and subtropical areas in which approximately 1.5 billion people are infected. A clear understanding of the epidemiology and distribution of diseases is an important aid for control and prevention. The aim of our study was to identify the effects of environmental and climatic factors on distribution patterns of STHs and to develop a risk map for STH infections under current environmental and climate regimes in Thailand. Geographical information systems (GIS), remote sensing, and Maximum Entropy (MaxEnt) algorithm software were used to determine the significant factors and to create predictive risk maps for STH infections in Thailand. The disease data from Thailand covered the years from 1969 to 2014, while environmental and climatic data were compiled from the Worldclim database, MODIS satellite imagery, Soilgrids and ISCGM. The models predicted that STHs occur mainly in southern Thailand. Mean annual precipitation was the factor most affecting the current distribution of A. lumbricoides, T. trichiura, and S. stercoralis. Land cover class was the main predictor for distribution of S. stercoralis and important for hookworms. Altitude was the dominant factor affecting the distribution of hookworms, and mean temperature of the wettest quarter was significantly associated with A. lumbricoides distribution. A predicted distribution map of STHs to identify environmental risk factors in Thailand is presented. This work provides a model for use in STH monitoring and health planning not only in Thailand but also in other countries with similar disease conditions.

Fecal parasite risk in the endangered proboscis monkey is higher in an anthropogenically managed forest environment compared to a riparian rain forest in Sabah, Borneo

Understanding determinants shaping infection risk of endangered wildlife is a major topic in conservation medicine. The proboscis monkey, Nasalis larvatus, an endemic primate flagship species for conservation in Borneo, is endangered through habitat loss, but can still be found in riparian lowland and mangrove forests, and in some protected areas. To assess socioecological and anthropogenic influence on intestinal helminth infections in N. larvatus, 724 fecal samples of harem and bachelor groups, varying in size and the number of juveniles, were collected between June and October 2012 from two study sites in Malaysian Borneo: 634 samples were obtained from groups inhabiting the Lower Kinabatangan Wildlife Sanctuary (LKWS), 90 samples were collected from groups of the Labuk Bay Proboscis Monkey Sanctuary (LBPMS), where monkeys are fed on stationary feeding platforms. Parasite risk was quantified by intestinal helminth prevalence, host parasite species richness (PSR), and eggs per gram feces (epg). Generalized linear mixed effect models were applied to explore whether study site, group type, group size, the number of juveniles per group, and sampling month predict parasite risk. At the LBPMS, prevalence and epg of Trichuris spp., strongylids, and Strongyloides spp. but not Ascaris spp., as well as host PSR were significantly elevated. Only for Strongyloides spp., prevalence showed significant changes between months; at both sites, the beginning rainy season with increased precipitation was linked to higher prevalence, suggesting the external life cycle of Strongyloides spp. to benefit from humidity. Higher prevalence, epgs, and PSR within the LBPMS suggest that anthropogenic factors shape host infection risk more than socioecological factors, most likely via higher re-infection rates and chronic stress. Noninvasive measurement of fecal parasite stages is an important tool for assessing transmission dynamics and infection risks for endangered tropical wildlife. Findings will contribute to healthcare management in nature and in anthropogenically managed environments.

Prevalence and molecular characterization of Strongyloides stercoralis, Giardia duodenalis, Cryptosporidium spp., and Blastocystis spp. isolates in school children in Cubal, Western Angola

BACKGROUND

Human infections by the gastrointestinal helminth Strongyloides stercoralis and the enteric protozoans Giardia duodenalis, Cryptosporidium spp. and Blastocystis spp. are not formally included in the list of 20 neglected tropical diseases prioritised by the World Health Organization. Although largely underdiagnosed and considered of lower public health relevance, these infections have been increasingly demonstrated to cause significant morbidity and even mortality globally, particularly among children living in resource-poor settings.

METHODS

In this cross-sectional survey the prevalence, frequency and molecular diversity of S. stercoralis, G. duodenalis, Cryptosporidium spp. and Blastocystis spp. were investigated in a school children population in the province of Benguela (Angola). A total of 351 stool samples were collected during January to June 2015. The presence of S. stercoralis and G. duodenalis was confirmed by qPCR methods. Giardia duodenalis assemblages and sub-assemblages were determined by multilocus sequence-based genotyping of the glutamate dehydrogenase and β-giardin genes of the parasite. Detection and identification of Cryptosporidium and Blastocystis species and subtypes was carried out by amplification and sequencing of a partial fragment of the small-subunit ribosomal RNA gene of both protozoan. Analyses of risk factors potentially associated with the transmission of these pathogens were also conducted.

RESULTS

Prevalences of S. stercoralis, G. duodenalis, Cryptosporidium spp., and Blastocystis spp. were estimated at 21.4% (95% CI: 17.1-25.7%), 37.9% (95% CI: 32.8-43.0%), 2.9% (95% CI: 1.1-4.5%) and 25.6% (95% CI: 21.18-30.2%), respectively. Overall, 64.1% (225/351) of the children were infected by at least one of the pathogens investigated. Sequence analyses of the 28 G. duodenalis isolates that were successfully genotyped allowed the identification of sub-assemblages AI (14.3%), AII (14.3%), BIII (7.1%) and BIV (25.0%). Discordant typing results AII/AIII and BIII/BIV were identified in 7.1% and 14.3% of the isolates, respectively. A total of five additional isolates (17.9%) were identified as assemblage B. Three Cryptosporidium species including C. hominis (70%), C. parvum (20%) and C. canis (10%) were found circulating in the children population under study. A total of 75 Blastocystis isolates were assigned to the subtypes ST1 (30.7%), ST2 (30.7%), ST3 (36.0%), ST5 (1.3%) and ST7 (1.3%), respectively. Children younger than seven years of age had significantly higher risk of infections by protozoan enteropathogens (PRR: 1.35, P < 0.01), whereas being underweight seemed to have a protective effect against these infections (PRR: 0.74, P = 0.005).

CONCLUSIONS

The burden of disease attributable to human strongyloidiasis, giardiosis, cryptosporidiosis and blastocystosis in Angola is considerably higher than initially estimated in previous surveys. Surveillance and control of these infections should be jointly tackled with formally considered neglected tropical diseases in order to maximize effort and available resources. Our data also demonstrate the added value of using molecular diagnostic methods in high transmission areas.

Different but overlapping populations of Strongyloides stercoralis in dogs and humans-Dogs as a possible source for zoonotic strongyloidiasis

Strongyloidiasis is a much-neglected soil born helminthiasis caused by the nematode Strongyloides stercoralis. Human derived S. stercoralis can be maintained in dogs in the laboratory and this parasite has been reported to also occur in dogs in the wild. Some authors have considered strongyloidiasis a zoonotic disease while others have argued that the two hosts carry host specialized populations of S. stercoralis and that dogs play a minor role, if any, as a reservoir for zoonotic S. stercoralis infections of humans. We isolated S. stercoralis from humans and their dogs in rural villages in northern Cambodia, a region with a high incidence of strongyloidiasis, and compared the worms derived from these two host species using nuclear and mitochondrial DNA sequence polymorphisms. We found that in dogs there exist two populations of S. stercoralis, which are clearly separated from each other genetically based on the nuclear 18S rDNA, the mitochondrial cox1 locus and whole genome sequence. One population, to which the majority of the worms belong, appears to be restricted to dogs. The other population is indistinguishable from the population of S. stercoralis isolated from humans. Consistent with earlier studies, we found multiple sequence variants of the hypervariable region I of the 18 S rDNA in S. stercoralis from humans. However, comparison of mitochondrial sequences and whole genome analysis suggest that these different 18S variants do not represent multiple genetically isolated subpopulations among the worms isolated from humans. We also investigated the mode of reproduction of the free-living generations of laboratory and wild isolates of S. stercoralis. Contrary to earlier literature on S. stercoralis but similar to other species of Strongyloides, we found clear evidence of sexual reproduction. Overall, our results show that dogs carry two populations, possibly different species of Strongyloides. One population appears to be dog specific but the other one is shared with humans. This argues for the strong potential of dogs as reservoirs for zoonotic transmission of S. stercoralis to humans and suggests that in order to reduce the exposure of humans to infective S. stercoralis larvae, dogs should be treated for the infection along with their owners.

Strongyloidiasis in a young French woman raises concern about possible ongoing autochthonous transmission in Spain

Strongyloidiasis is one of the most common geohelminth infections in tropical and subtropical areas. Accurate diagnosis remains challenging, leading to an overall underestimation of strongyloidiasis prevalence. The possibility of ongoing autochthonous transmission in some temperate areas and especially in southern Europe is still debated, and data supporting this hypothesis are scarce. The case of a young French woman, who had travelled frequently to Spain and had acquired Strongyloides stercoralis infection as revealed by gastrointestinal symptoms and hypereosinophilia, is reported here. Physicians should keep in mind the risk of being infected in some areas of southern Europe, even if low, in order to avoid the life-threatening manifestations of strongyloidiasis favoured by pathological or therapeutic immunosuppression.

Exposure of medical staff to Strongyloides stercolaris from a patient with disseminated strongyloidiasis

We examined whether medical staff were infected with Strongyloides stercolaris through exposure to the body substances of a patient with disseminated strongyloidiasis. The patient excreted a large number of S. stercolaris organisms in respiratory secretions and stool-like excretions from a nasogastric tube. Blood tests in six physicians and three nurses, who were highly suspected of having had contact with the substances without appropriate protection during medical care of the patient for about 1 week, showed no increase of eosinophiles or IgG antibodies against S. stercolaris. We conclude that adherence to the standard precautions is sufficient for preventing the nosocomial transmission of this organism.

Infection of naïve, free-living brushtail possums (Trichosurus vulpecula) with the nematode parasite Parastrongyloides trichosuri and its subsequent spread

Despite the importance of spatial processes in host-parasite interactions, parasite dispersal has been the subject of few experimental studies. Introduced marsupial common brushtail possums (Trichosurus vulpecula) are a major environmental and agricultural pest in New Zealand. Parastrongyloides trichosuri, an intestinal rhabdiasoid nematode parasite specific to possums, is being evaluated as a self-disseminating delivery system for engineered fertility control vaccines. This study addressed whether an artificial infection could be established in a naïve, free-living possum population, by measuring the post-release dynamics of possum-parasite interactions at the release site, and by following the spread of the parasite into surrounding possum populations. Infection was established efficiently by applying infective larvae to the skin of possums on a single occasion. All experimentally infected possums recaptured 3 weeks after infection had parasite eggs in their faeces. Over the subsequent 2.5 years, infection spread steadily over an area of about 6000 ha. Infection persisted at the original release site for the 3.5 years of the study and at a nearby site infected by natural spread for more than 3 years. Seasonal changes in faecal egg counts were similar at the two sites. The rapid establishment of the parasite and its spread provide additional support for its ongoing development as a vaccine delivery system.

No evidence for specificity between host and parasite genotypes in experimental (Nematoda) infections

A key requirement for several theories involving the evolution of sex and sexual selection is a specificity between host and parasite genotypes, i.e. the resistance of particular host genotypes to particular parasite genotypes and the infectivity of particular parasite genotypes for particular host genotypes. Determining the scope and nature of any such specificity is also of applied relevance, since any specificity for different parasite genotypes to infect particular host genotypes may affect the level of protection afforded by vaccination, the efficacy of selective breeding of livestock for parasite resistance and the long-term evolution of parasite populations in response to these control measures. Whereas we have some evidence for the role of specificity between host and pathogen genotypes in viral and bacterial infections, its role in macroparasitic infections is seldom considered. The first empirical test of this specificity for a vertebrate-nematode system is provided here using clonal lines of parasite and inbred and congenic strains of rat that differ either across the genome or only at the major histocompatibility complex. Although significant differences between the resistance of host genotypes to infection and between the fitness of different parasite genotypes are found, there is no evidence for an interaction between host and parasite genotypes. It is concluded that a specificity between host and parasite genotypes is unlikely in this system.

[Autochthonous strongyloidosis in an 81-year-old woman]

Strongyloidosis is an parasitic disease, caused by an intestinal nematode endemic in tropic and subtropic regions. In Central Europe it occurs only sporadically. The infective larvae in the soil penetrate the human skin. Following circulation through the lungs the larvae settle in the small intestine and mature into adult worms. Chronic strongyloidosis recurring up to 15 years is possible through endogenous autoinfection. Clinical feature of the disease are gastrointestinal symptoms, hypereosinophilia and skin rashes. We describe the case of an 81-year-old woman who presented with scaly exanthema, fever and perianal fistulation. A microscopic examination of a stool sample demonstrated filariform larvae of Strongyloides stercoralis. An autochthonous mode of infection was assumed. After starting treatment with mebendazole eosinophilia and rash gradually disappeared. The laboratory finding of eosinophilia in patients with gastrointestinal symptoms or exanthema should prompt the differential diagnosis of a parasitosis. Stool examination is necessary to find rare autochthonous infections by intestinal nematodes. Pathogenesis, clinical manifestation and treatment of strongyloidosis are discussed along with the clinical picture.

Transmammary transmission of Strongyloides stercoralis in dogs

Vertical transmission of larvae is a major pathway in the life cycle of several species of Strongyloides, but evidence for it occurring in humans or dogs with Strongyloides stercoralis is absent. In an effort to determine if vertical transmission could occur with S. stercoralis, each of 3 female dogs was infected with filariform larvae at a different stage of the reproductive cycle, i.e., preconception, gestation, or postpartum. Results showed that none of 6 pups born to a female infected before conception or any of 6 pups born to another female infected during gestation harbored any stage of S. stercoralis when necropsied at parturition. Conversely, all 5 pups that nursed from the female infected immediately postpartum became infected with adult S. stercoralis in their small intestines (range, 56-129 adult worms). Significantly, live filariform larvae of S. stercoralis were observed on 2 different occasions from milk samples taken from the lactating female. Because arrested development of larvae is not known in S. stercoralis, there is no reservoir of larvae in the parenteral tissues of females to queue for passage to the pups and, thus, it is not surprising that only timely infections, perhaps very late in gestation and during lactation, can be successful. These data support previous work in dogs with S. stercoralis, which concluded that vertical transmission through prenatal pathways does not occur, but they are the first from the dog to indicate that vertical transmission of this parasite through transmammary routes is possible. Whether transmammary transmission of S. stercoralis occurs in humans remains unknown but given its immense pathological potential, it should not be overlooked.

Human strongyloidiasis in AIDS era: its zoonotic importance

Human strongyloidiasis is caused by a nematode Strongyloides stercoralis. Many species cause strongyloidiasis in animals. The parasite has predilection to one host only but the host specificity is not strict. When animal species infects humans there is intense allergic reaction in the form of cutaneous larva currens and larva migrans. Therefore, strongyloidiasis in strict terms is a zoonotic disease. The strongyloides species have three stages. The parasitic form inside the host, the free form stage in the soil or water that moults to infective third stage. The later infects the host through skin and migrate to the heart and lung and finally swallowed back to cause intestinal infection. However, in some cases intense pulmonary manifestations may take place. The Strongyloides stercoralis has unique feature of moulting from parasitic form to infective stage within the body, rather than coming out and forming free living stage and causing autoinfection. This may lead to latent infection for indefinite period in an immunocompetant person but fatal hyper or disseminated infection in immunocompromised person like patients of AIDS, organ transplant recipients, cancer and other patients put on immunosuppressive therapy, in whom it can involve any organ of the body. Because this group of patients in last few years have increased tremendously in Africa and South-East Asia, more and more cases of strongyloidiasis are being reported in english literature. The diagnosis of intestinal strongyloidiasis is made by repeated stool smear examinations and in extraintestinal strongyloidiasis the appropriate specimen is examined for the rhabditiform larvae. Recently serological tests have also been developed that can be used for epidemiological purposes. The drug of choice for the treatment of strongyloidiasis remains thiabendazole but due to its unacceptable side effects other medicines like albendazole and ivermectine are being used more frequently. The prevention of the infection is possible by adopting good personal hygiene and safe drinking water supply.

The risk of Strongyloides stercoralis transmission from patients with disseminated strongyloidiasis to the medical staff

To assess the risk of Strongyloides stercoralis transmission from two patients with disseminated strongyloidiasis to medical staff who had been in close contact with the patients, blood and stool specimens were obtained from medical staff two to three months after close contact with the patients. Antibodies to S. stercoralis were determined in blood. Stool specimens were tested for parasites with three different procedures.Forty-one medical staff were included. Culture and stool examination were negative in all subjects. Serology was negative in all subjects but one who had a borderline titer without signs or symptoms of strongyloidiasis. No evidence of transmission of S. stercoralis from patients with disseminated strongyloidiasis to medical staff was found.

Transmission of Strongyloides steracolis person to person

A case of presumed person-to-person transmission of Strongyloides steracolis is described. The index case was immunocompromised following high dose glucocorticosteroid therapy for myelodysplasia, which resulted in reactivation of latent strongyloides infection with the hyperinfestation syndrome. Physicians unfamiliar with this disease should realize that a history of foreign travel is unnecessary to acquire this parasite, and that transmission to persons in close proximity to the index case does occur and warrants treatment.

[Strongyloidosis. Part VII. Epidemiology and prevention (2)]

The formation of Strongyloides stercoralis infections in the tropical countries and in the temperate climatic zone, with special attention to the factors and the high risk groups, were described. The concurrent infections, prevention and control of strongyloidosis was also presented.

Chemo- and thermosensory neurons: structure and function in animal parasitic nematodes

Nematode parasites of warm-blooded hosts use chemical and thermal signals in host-finding and in the subsequent resumption of development. The free-living nematode Caenorhabditis elegans is a useful model for investigating the chemo- and thermosensory neurons of such parasites, because the functions of its amphidial neurons are well known from laser microbeam ablation studies. The neurons found in the amphidial channel detect aqueous chemoattractants and repellants; the wing cells-flattened amphidial neurons-detect volatile odorants. The finger cells-digitiform amphidial neurons-are the primary thermoreceptors. Two neuron classes, named ADF and ASI, control entry into the environmentally resistant resting and dispersal dauer larval stage, while the paired ASJ neurons control exit from this stage. Skin-penetrating nematode parasites, i.e. the dog hookworm Ancylostoma caninum, and the threadworm, Strongyloides stercoralis, use thermal and chemical signals for host-finding, while the passively ingested sheep stomach worm, Haemonchus contortus, uses environmental signals to position itself for ingestion. Amphidial neurons presumably recognize these signals. In all species, resumption of development, on entering a host, is probably triggered by host signals also perceived by amphidial neurons. In the amphids of the A. caninum infective larva, there are wing- and finger-cell neurons, as well as neurons ending in cilia-like dendritic processes, some of which presumably recognize a sequence of signals that stimulate these larvae to attach to suitable hosts. The functions of these neurons can be postulated, based on the known functions of their homologs in C. elegans. The threadworm, S. stercoralis, has a complex life cycle. After leaving the host, soil-dwelling larvae may develop either to infective larvae (the life-stage equivalent of dauer larvae) or to free-living adults. As with the dauer larva of C. elegans, two neuron classes control this developmental switch. Amphidial neurons control chemotaxis to a skin extract, and a highly modified amphidial neuron, the lamellar cell, appears to be the primary thermoreceptor, in addition to having chemosensory function. The stomach worm, Haemonchus contortus, depends on ingestion by a grazing host. Once ingested, the infective larva is exposed to profound environmental changes in the rumen. These changes stimulate resumption of development in this species. We hypothesize that resumption of development is under the control of the ASJ neuronal pair. Identification of the neurons that control the infective process could provide the basis for entirely new approaches to parasite control involving interference with development at the time and place of initial host-contact.

A second peak of egg excretion in Strongyloides ratti-infected rats: its origin and biological meaning

In Strongyloides ratti-infected rats, 2 peaks of egg excretion were observed; a large one with maximum egg production on days 7-8 of infection and a small more inconspicuous one around day 25. The second peak, which had been ignored in most studies, was produced by adults in the caecum and the colon. The adults were larger in length and had more embryonated eggs in the uterus compared with adults in the small intestine at day 25 post-infection. It is suggested that parasitic adults once expelled from the small intestine resettle and recover in the large intestine. Filter paper faecal culture carried out for 9 days at different days post-infection revealed that the total number of infective larvae that developed during the second peak was twice the number that developed during the first peak, despite the fact that total egg output during the second peak was less than one twentieth of the first peak. The results suggest that the small second peak was as important as the first one in the transmission of S. ratti.

Heterogeneity in the distribution of Strongyloides ratti infective stages among the faecal pellets of rats

The distribution of helminth parasites within their host population is usually overdispersed and can be described by the negative binomial distribution. The causes of this overdispersion are poorly understood, but heterogeneity in the distribution of infective stages within the environment has been implicated as a possible factor. Here we describe the distribution of infective stages of the rat intestinal nematode parasite Strongyloides ratti among the faecal pellets of its host. The distribution of infective stages between faecal pellets is overdispersed and well described by the negative binomial distribution. This overdispersion increases during the course of infection and occurs over a range of infection intensities. Overdispersion of nematode infective stages among faecal pellets may result in increased spatial heterogeneity of the infective stages in the environment and thus may contribute to the generation of overdispersion of adult parasitic stages. In addition, these findings raise important issues regarding the accurate quantification of helminth egg counts from faecal samples.

Strongyloides hyperinfection in a renal transplant recipient receiving cyclosporine: possible Strongyloides stercoralis transmission by kidney transplant

Strongyloides hyperinfection and dissemination are recognized complications in kidney allograft recipients; however, the development of strongyloidiasis in renal transplant recipients receiving cyclosporine A (CyA) has not been described, nor has the development of strongyloidiasis in other organ transplant recipients. The former observation has been attributed to the antiparasitic activity of CyA seen in animal studies; the latter has no explanation yet. We report the first case of Strongyloides hyperinfection in a renal transplant patient occurring immediately after CyA was discontinued. From the unique characteristics of this case, it appears that the anti-Strongyloides activity of CyA in animals may also be found in humans.

A case of systemic strongyloidiasis in an ex-coal miner with idiopathic colitis

An ex-coal miner was diagnosed with an idiopathic sigmoiditis compatible with colitis ulcerosa. He was treated with corticosteroids because of his deteriorating clinical condition, but his condition continued to worsen. He revealed to have a systemic Strongyloides stercoralis hyperinfection and Strongyloides colitis. A short time after diagnosis he died from septic shock despite therapy with thiabendazole and antibiotics. S. stercoralis is an opportunistic infection that is not uncommon and has high mortality in hyperinfection. It is prevalent in (sub)tropical areas, and also in coal mines because of the specific microclimate. However, the parasite is difficult to detect because eosinophilia can appear normal in chronic infection. Several stool examinations, duodenal aspiration or biopsies are necessary for a high diagnostic sensitivity. Serological diagnosis is the most sensitive and specific but is not always available.

Household aggregation of Strongyloides stercoralis infection in Bangladesh

Strongyloides stercoralis infections were shown to be aggregated in households in an urban slum community in Dhaka, Bangladesh. Parasitological data on 880 residents living in 280 households were analysed statistically using 3 different tests, each of which yielded significant evidence of household aggregation of S. stercoralis infection. One test was applied to the data after stratification for 4 variables were previously shown to be independently associated with infection. Evidence of household aggregation of infection remained after stratification, suggesting that aggregation is due not only to shared risk factors, but also to either familial genetic predisposition to infection or close contact person to person transmission of infection within households.

Strongyloides stercoralis: the first rodent model for uncomplicated and hyperinfective strongyloidiasis, the Mongolian gerbil (Meriones unguiculatus)

Strongyloidiasis is the most common endemic helminthiasis in several of the world's industrialized nations, yet relatively little is known about its basic biology and immunobiology because a practical rodent model for the investigation of this clinically important parasitism is lacking. This study reports such a model for use in the investigation of Strongyloides stercoralis infection. Normal male gerbils infected subcutaneously with 1000 infective filariform larvae harbored moderate numbers (83.6 +/- 27.6) of adult worms at 35 days after infection, and a low-grade infection persisted for at least 131 days mimicking the chronicity of human infections. Gerbils treated weekly with 2 mg of methylprednisolone acetate developed hyperinfective strongyloidiasis with up to 8000 autoinfective larvae occurring in these animals at postinfection day 21. Autoinfection never occurred in normal (untreated) gerbils.

[Natural parasitism of buffaloes in Botucatu, SP, Brazil. III. Dynamics of gastrointestinal parasitism in cows and their calves]

Gastrointestinal parasitism of 24 buffalo cows before parturition, and post-parturition, their infection and that of their respective calves during the following 30 weeks were studied. Willis, Hoffmann and whenever possible, the modified Gordon & Whitlock techniques were used for fecal examinations. Toxocara vitulorum eggs were the earliest forms encountered in calves feces, as follows: during the 1st week after birth, 58.33% of the calves were positive, and in the 4th week, 100% of these animals were positive. Eggs of Strongyloides sp were in the 1st week after birth in two of the calves and in the 5th week, all for them were positive. The next parasites to appear were the Coccidia of which oocysts were detected in the feces of two calves in the 2nd week after birth, and 58.33% of the calves were positive for these in the 3rd week, and in the 6th week, all calves shed oocysts in their feces. On the other hand, eggs of Strongyloides were the last forms to appear in calves feces. However, despite their sporadic appearance in the feces, eggs of these parasites were observed continuously from the 11th week onwards, and at this point, the percentage of positive samples began to increase to reach its peak. Relatively to adult animals, eggs of T. vitulorum were observed in the feces of 11 cows, one or twice at most; eggs of Strongyloides sp were seen only once in the feces of four buffalo cows and eggs of Strongyloides in 21 out of 24 cows. Oocysts of Coccidia were observed in 16 cows. Mechanisms of infestation of calves with these parasites are discussed.

Transmission of intestinal helminths in Danish sow herds

Faecal samples from sows and their litters, all untreated with anthelmintics, were examined in eight sow herds, ranging from very intensive to very traditional management. Four helminth genera were recorded, namely Oesophagostomum sp., Ascaris suum, Trichuris suis and Strongyloides ransomi. The herds with the most intensive management were only infected with A. suum, while the more traditionally managed herds were infected with three or four species. In one herd, the sows showed a small relative increase in the excretion of Oesophagostomum eggs during lactation, but in general there was no consistently observable peri-parturient increase in faecal egg output. Furthermore, faecal examination of 5-12-week-old pigs indicated that sow-to-piglet transmission was important in the traditionally managed herds, while it was negligible in the intensive herds. A seasonal variation in the excretion of Oesophagostomum sp. and A. suum eggs was observed in the youngest pigs in the traditional herds, with the highest faecal egg counts occurring in the summer and autumn. However, this pattern became indistinct during the fattening period and did not exist in the sows, except for A. suum infections in the heavily infected traditional herds. The helminths egg excretion in the intensive herds did not show any seasonal variation.

[The current situation with strongyloidiasis in the USSR]

The literary data available and our own observations served the basis for characterization on strongyloidiasis distribution areas in the USSR. They embrace the Caucasus, Middle Asia, the European part of the country up to latitude 55-56 degrees north in the Maritime Territory and the southern part of the Khabarovsk Territory. Intensive invasion foci in specialized hostel-type institutions, invasion importation from the tropics to moderate climatic zones and their role in the epidemic process are discussed.

Transmammary transmission of Strongyloides ratti

The rate of transmammary transmission of Stronglyloides ratti was examined in albino rats in terms of the route of subcutaneous (s.c.) migration from the infection site (the skin) to the cranium. Inoculation sites nearer the cranium resulted in less frequent transmammary infection. The maximum number of adult worms was recovered from the sucklings when the mother was inoculated in her hindquarter and sucklings were allowed to feed for 30-36 h after inoculation (AI). Few worms were recovered from sucklings when they were allowed to nurse during periods of less than 24 h AI or greater than 42 h AI. In lactating mothers, larval infection of the mammary glands was commonly observed, and these larvae showed an increased esophagus length. In nonlactating mothers, most larvae completed their migration to the cranium within 36 h AI.

Strongyloides stercoralis hyperinfection in a patient with the acquired immune deficiency syndrome

Severe infections with Strongyloides stercoralis occur in immunocompromised patients. Strongyloides hyperinfection syndrome complicated by gram-negative bacteremia and meningitis in a bisexual man with the acquired immune deficiency syndrome (AIDS) is described. Increased awareness of this infection, which may also be sexually transmitted, is recommended when caring for patients with AIDS who are homosexual, or have resided in areas endemic for strongyloidiasis. Multiple stool examinations should be performed routinely for such patients. Examination of sputum for the parasite is recommended if pneumonia is present. Prompt diagnosis and therapy are essential for prevention of fatal dissemination.

The effect of method of infection on the pathway of juvenile Strongyloides ratti in the host

Subcutaneous injection of the larvae is the almost universally adopted means of initiating experimental infections of skin-invading roundworms but, so far, the possibility that this procedure introduces artefacts of one kind or another has not been critically studied. Experiments described in this paper were used to compare the effect of (a) injection and (b) skin application, of a small, precisely counted ('exact') dose of larvae. Results with two strains of S. ratti showed that the same proportion of the dose developed to adults in the intestines of rats irrespective of the method. With the same exact dose technique it has been shown that milk-borne infection of the pups of lactating rats is not an artefact produced by injection. Large doses (mean 4000) of larvae of the homogonic strain of S. ratti carrying a radioactive label of 75Se were tracked in their migration to the mammary gland following injection or skin application at two different sites on the right-hand side of nursing mother rats. The broad conclusion of earlier work in this laboratory using injection, that larvae move by a local route and not a systemic one, was supported by the results. The detailed distribution of the label and of unlabelled worms of the heterogonic strain in families was, however, different for the two methods, indicating that subtle variations in pathway can be brought about by the use of injection. If migration involves the lymphatic system, then the interpretation of immunological experiments in terms of lymphatic anatomy must take account of such procedural effects. The extent to which these results contribute to theories of migration in Strongyloides ratti is discussed.

Efficacy of ivermectin against somatic Strongyloides ransomi larvae

The efficacy of ivermectin against the somatic larval stages of Strongyloides ransomi was evaluated in three trials involving 35 pregnant gilts harbouring induced infections. Treatment at a rate of 300 micrograms/kg bodyweight subcutaneously, four to 16 days before farrowing, was highly effective as judged by counts of larvae in milk and worm burdens of piglets.

Loss of surface coat by Strongyloides ratti infective larvae during skin penetration: evidence using larvae radiolabelled with 67gallium

The optimal conditions for labelling infective larvae of Strongyloides ratti with 67gallium citrate were determined. Radiolabelled larvae were injected s.c. into normal and previously infected rats. The distribution of radioactivity in these animals was compared with that in rats infected subcutaneously with a similar dose of free 67Ga by using a gamma camera linked to a computer system. Whereas free 67Ga was distributed throughout the body and excreted via the hepatobiliary system, the bulk of radioactivity in rats injected with radiolabelled larvae remained at the injection sites. Direct microscopical examination of these sites, however, revealed only minimal numbers of worms. When rats were infected percutaneously with radiolabelled larvae, it was found that most radioactivity remained at the surface, despite penetration of worms. When infective larvae were exposed to CO2 in vitro and examined carefully by light microscopy, loss of an outer coat was observed. It was concluded that infective larvae lose an outer coat on skin penetration.

Sexually transmitted viral hepatitis and enteric pathogens

Hepatitis viruses, enteric pathogens, and anorectal infections may commonly be transmitted by various sexual practices. Because of their larger numbers of sexual partners and sexual practices such as anilingus and anal intercourse, homosexual men are at particularly high risk of acquiring hepatitis B, giardiasis, amebiasis, shigellosis, campylobacteriosis, and anorectal infections with Neisseria gonorrhoeae, Chlamydia trachomatis, Treponema pallidum, herpes simplex virus, and human papilloma viruses. The evidence for sexual transmission of these infections as well as their diagnosis and treatment are discussed.

Induction of immunity by transcolostrally-passed Strongyloides ransomi larvae in neonatal pigs

Earlier studies had suggested that neonatal pigs that acquire infections of Strongyloides ransomi via the sow's milk fail to expel intestinal worms normally. Adult worm recoveries were compared from the intestines of normal and transcolostrally-infected neonatal pigs after a subcutaneous challenge inoculation of third-stage larve (L3) to determine whether a direct intestinal infection (via sow's colostrum) might affect resistance. Additionally, transcolostrally-infected pigs that had received an additional subcutaneous inoculation of L3 were reinoculated with L3, and the adult worm recoveries were compared to those of pigs immunized with only one subcutaneous inoculation of L3 to determine the effect of initial transcolostral infection on the development of protective immunity by this established procedure. The results showed that intestinal worms obtained transcolostrally can induce high resistance in pigs to reinfection by S. ransomi, and they do not affect the enhancement of protective immunity by a subcutaneous inoculation of L3. However, peripheral blood lymphocytes obtained from transcolostrally-infected pigs did not respond to larval antigens in vitro until after a subsequent subcutaneous inoculation of L3.

Strongyloidiasis: is it transmitted from husband to wife?

The possible transmission of Strongyloides stercoralis from men who had been infected for many years to their wives was investigated. None of the 24 wives was infected, as indicated by the absence of anti-Strongyloides antibodies in their serum. Thus, the risk of transmission from husband to wife seems small, although the likelihood among homosexuals is greater.