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Background Current treatment options for onchocerciasis are sub-optimal, prompting research and development of a safe cure (macrofilaricide). Onchocerca ochengi, a parasite of cattle, is used as a close surrogate for the human parasite O. volvulus in a murine model for pre-clinical screening of macrofilaricides. Skin from naturally infected cattle have been used in previous studies as a reliable source of parasite material. However, there is limited knowledge on how source-related factors such as the microfilaridermia status of the cattle, the nodule load and nodular worm viability may affect survival of male O. ochengi worms implanted in the rodent hosts. Such relationships were investigated in this study. Methods Dermal tissue and nodules were obtained from Gudali cattle, dissected and cultured to obtain migrating microfilariae (mf) and male worms. Emerged male worms were implanted into SCID mice and Gerbils (Meriones unguiculatus) and recovery rates were determined upon 42 days post implantation. Finally, nodules were processed for histology and embryogram analyses to assess the nodular worm viability and fertility, respectively. Results Of the 69 cattle sampled, 24 (34.8%) were mf+ and 45 (65.2%) were mf–. The mean nodule loads were 180.5 ± 117.7 (mf+) and 110.6 ± 102.7 (mf-) (p = 0.0186). The mean male worm harvest from nodules were 76.8 ± 120.3 and 47.2 ± 33.4 (p = 0.2488) for mf+ and mf– cattle, respectively. The number of male worms per 100 nodules were 57/100 and 46/100 nodules for mf+ and mf– cows, respectively. Female worms from nodules of mf– cows had higher counts of both normal and abnormal embryos with higher proportions of dead nodular worms evinced by histology compared to those from mf+ cows. A total of 651 worms were implanted into mice and gerbils, out of which 129 (19.81%) were recovered. Logistic regression analysis indicated that the microfilaridermia status of the cattle (presence of mf) (OR = 4.3319; P = 0.001) is the single most important predictor of the success of male worm recovery after implantation into rodents. Conclusion Microfilaridermic cattle provide a promising source of adult O. ochengi. Male worms from this group of cattle have a better success rate of survival in a murine implant model. Nevertheless, in the programmatic point of view, amicrofilaridermic Gudali cattle would still constitute an important source of O. ochengi male worms with relatively good viability after implantation into rodents., Graphical abstract Image 1, Highlights • There is a need of developing safe macrofilaricide for human onchocerciasis using cattle Onchocerca ochengi. • Skin from naturally infected cattle have been used as a reliable parasite source for development of murine pre-clinical screening models. • The role of source-related factors on O. ochengi production and the success of pre-clinical screening models is assessed. • Worms from positive microfilaridermic cattle are successfully recovered after their implantation into rodents.

We report a 20-year-old male with a past history of diarrhea and discharge of a strobila of a broad tapeworm from his anus 3 months ago. He again noticed passing a tapeworm strobila and he visited our hospital with the tapeworm sample. The macroscopic appearance and the pathological features strongly suggested Diphyllobothriasis. Soon after the first visit to our hospital, a capsule endoscopy was performed with the result of no evidence of strobilae or scoleces. Praziquantel at 20 mg/kg was orally administered once. Before drug administration, egg-like structures were present in the stool. They disappeared soon after drug administration. In human Diphyllobothriasis, Dibothriocephalus nihonkaiensis (D. nihonkaiensis) infection and Dibothriocephalus latus (D. latus) infection are common. These two species are morphologically similar but genetically distinct. Accordingly, polymerase chain reaction (PCR) using genomic DNA of the tapeworm infecting our case was performed for amplifying mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. The amplified DNA fragment by PCR of our case was phylogenetically compared with other mitochondrial cox1 gene sequences of D. nihonkaiensis, D. latus, D. dendriticus, Taenia saginata, Taenia solium and Spirometra erinaceieuropaei. As a result, the tapeworm of our case was most likely within the spectrum of D. nihonkaiensis. Although human diphyllobothriasis is not a life-threatening disease for human beings, it has become a re-emerging problem even in the most developed countries with the increasing popularity of eating raw fish. The knowledge of how to cook or freeze raw fish before eating can reduce the risk of infection. However, without general awareness of human parasite infection, food-borne infections will continue to be a public health problem. Keywords: Tapeworm, Dibothriocephalus nihonkaiensis, Dibothriocephalus latus, Mitochondrial cytochrome c oxidase subunit 1 gene, Praziquantel

In comparison with other helminths that afflict humans on a global scale, Ascaris lumbricoides and ascariasis are relatively under-researched in terms of the proteins and other products to which the parasites expose their hosts. The reputation of the parasite as a source of potent allergens, and the recognition that immune hypersensitivity in the lung caused by migrating larvae is a significant problem, has served to focus attention on immune responses to Ascaris. Research has increasingly focused on the parasite’s products and responses to them in experimental rodents, and in pigs as permissive hosts for the full life-cycle of Ascaris suum. In parallel, immunoepidemiology of ascariasis in humans has been developing, often aimed at understanding how the infection polarizes immune responses. This review deals with the antigens of the parasite, how the immune repertoire to them varies dramatically between infected humans, the genetic loci that are probably involved, and its unpredictability. New work on the molecular structure of the unusual proteins produced by Ascaris and other nematodes is also covered, including the well-known ABA-1 allergen. Emphasis is also placed on a poorly understood aspect of Ascaris immunobiology, prompted by a few tantalizing observations, namely the potential diversity of surface and secreted antigens of the human parasite, and how such polymorphisms could be crucial to understanding the chronicity of ascariasis in the face of continuous loss and recruitment of the parasites themselves.

Trypanosoma cruzi is a human parasite found in 200 wild and domestic animal species, some of which are used as experimental models and some may act as reservoirs. Studies of the various aspects of the human disease required numerous experimental models. Mice and rats lineages are useful for short-term studies of clinical aspects, immune, autoimmune, or chemotherapeutic responses. Long-term cardiac signs, histopathological and chemotherapeutic aspects were successfully investigated in dogs; monkeys, although expensive, have been used to study histopathological aspects and clinical manifestations. Choice of an experimental model is based on the knowledge acquired after one century of research on this theme. Transmission, clinical manifestation, and prevalence of T. cruzi in livestock are poorly described due to low sensitivity and specific diagnosis methods. However, its presence in livestock, peridomestic or wild species, was demonstrated. Peroral contamination seems dominant, involving vectors as passive intermediary hosts or as source of “food-borne disease.” Indeed, even in humans, recent outbreaks occurred by peroral contamination (fruit juice) in Brazil. Increasing presence of T. cruzi in the southern USA (wildlife, dogs, and triatomines) is a real threat for humans, which might turn to an emerging disease if a vicariant vector is found further north.

Publisher Summary Several groups of protists are different in their metabolic organization from most eukaryotic cells, including cells of multicellular animals. They lack an organelle with the typical energy conservation processes of mitochondria: they are amitochondriate. This chapter illustrates amitochondriate core metabolism by exemplifyingfour extensively studied human parasite species. The chapter focuses on the biochemical aspects of the overall core and energy metabolism. The chapter discusses extensive biochemical and sequence informationfor a number of individual enzymes involved but these are mentioned only if relevant to specific aspects of the overall metabolism. The description of core metabolism of a few amitochondriate parasitic protists demonstrates that these organisms are highly divergent from most eukaryotes with typical mitochondria, including their mammalian hosts. This divergence is apparent not only in the metabolic consequences of the absence of mitochondria, but also in the presence of processes and enzymes found only exceptionally in other eukaryotes.

Publisher Summary This chapter analyzes the interrelationships between Epstein-Barr herpes virus (EBV) and primates other than man. It also discusses the aspects of the discovery of the virus, its association with Burkitt lymphoma, infectious mononucleosis, and nasopharyngeal carcinoma, and its biologic properties studied in vitro . The studies of EBV in nonhuman primates have been useful in many respects. They have provided clues about the evolution of this highly adapted human parasite. Infection of nonhuman primate cells in vitro has yielded a regular source of cell-free virus for laboratory studies and has also clearly demonstrated the importance of host-specified control mechanisms in the regulation of the expression of viral information in transformed cells. The experimental infection of primates was successful once adequate amounts of transforming virus were available and once the virus host range was better defined by the means of in vitro transformation. Subsequent study allowed a direct demonstration of the capacity of EBV to cause lymphoreticuloproliferative disease. The identification of susceptible primate hosts now offers promise of the detailed analysis of the pathogenesis of EBV-induced disease and of the comparison of the pathogenic properties of different EBV-related viruses.

Publisher Summary This chapter discusses the evasion of immunity by nematode parasites causing chronic infections. Human nematode infections are long-lasting (chronic), and people living in endemic areas may become infected in early childhood and carry worms for the remainder of their lives. This chapter considers those aspects of the immunological relationship between host and parasite, in field and laboratory studies, that are pertinent to an understanding of the mechanisms by which immunity is avoided and thus, chronicity of infection achieved. Human parasite epidemiologists, veterinary parasitologists, parasite biologists, and immunologists all have an interest in the strategies employed by parasites to evade host immune responses and also in control measures aimed at breaking the transmission of these important pathogens. Much remains to be accomplished in this challenging area of parasite immunology, and a closer liaison between all research groups interested in chronic nematode parasites ensures rapid progress in the near future.

Publisher Summary Malaria is one of the world's most devastating diseases. Its intermittent fevers have been recognized since the beginning of recorded history. Because the parasites that cause malaria are very small, it was not possible to detect these pathogens until after the invention of the microscope. About five years after the finding of the human malaria parasites, birds were found also to be infected with malaria. But it was not until 1898 that malaria was seen in monkeys. It seems odd that bird malarias were found before the monkey malarias and that there was a lapse of 18 years from the discovery of the human parasite until they were found in these lower primates, animals that are recognized to have many similarities to man. Some scientists believe that some of the malarias of man and monkey are the same species, viz., P. malariae of man is the same as P. brasilianum of the Western Hemisphere monkeys. There are many important problems that can, should, and probably will be investigated in this new monkey host–human parasite model. However, the major difficulties have to do with the supply of the experimental animals, both quantitatively and qualitatively.

Publisher Summary This chapter describes fluorescent antibody (FA) studies in experimental malarias focusing on Simian–Human malaria antibody relationship. The six patients analyzed were infected only with P. falciparum or P. malariae. The FA responses are average values from 3 to 7 serum samples from each patient, adjusted so that the highest titer against the human parasite is equal to 100. The first three patients had P. falciparum only; it was seen that there were significant titers when P. fieldi antigen was used, as well as other minor cross reactivity. The three patients with P. malariae only also showed significant titers to P. fieldi, and even higher titers to P. brasilianum. This latter is of considerable interest, in that both P. malariae and P. brasilianum are quartan parasites and P. brasilianum has been shown to be infective to humans under experimental conditions. This immunologic cross-reactivity appears to be further indication of a close relationship between these two species. Minor cross-reactions with the other simian and human species were also seen.