Water-related parasitic diseases in China.

Water-related parasitic diseases are directly dependent on water bodies for their spread or as a habitat for indispensable intermediate or final hosts. Along with socioeconomic development and improvement of sanitation, overall prevalence is declining in the China. However, the heterogeneity in economic development and the inequity of access to public services result in considerable burden due to parasitic diseases in certain areas and populations across the country. In this review, we demonstrated three aspects of ten major water-related parasitic diseases, i.e., the biology and pathogenicity, epidemiology and recent advances in research in China. General measures for diseases control and special control strategies are summarized.

Invasion of different cell types by sporozoites of Eimeria species and effects of monoclonal antibody 1209-C2 on invasion of cells by sporozoites of several apicomplexan parasites.

Sporozoites of avian Eimeria species differed markedly in their ability to invade cells in vitro. Invasion by E. tenella and E. adenoeides was significantly greater in baby hamster kidney (BHK) and chicken cecal cell (CC) cultures than in primary chicken (PCK) or turkey kidney (PTK) cell cultures. Moreover, invasion of BHK cell cultures by E. adenoeides was significantly greater than that of other Eimeria species, and invasion by E. acervulina sporozoites was significantly lower. Monoclonal antibody 1209-C2 (MAb 1209-C2) reacted by immunofluorescent labeling (IFA) with refractile bodies of sporozoites of 5 species of Eimeria and Caryospora bigenetica, but not with sporozoites of Toxoplasma gondii, Hammondia hammondi, or Cryptosporidium parvum, which have no refractile bodies. The MAb also cross-reacted with formalin-fixed BHK, CC, turkey cecal (TC) cells, and PTK. Pretreatment of BHK cells with MAb 1209-C2 significantly reduced invasion of the cells by sporozoites of E. tenella, E. acervulina, E. meleagrimitis, and C. bigenetica, but did not alter invasion by T. gondii, C. parvum, or H. hammondia. Apparently, reactivity of MAB 1209-C2 with the sporozoites was required for inhibition of invasion despite the fact that the inhibition resulted from pre-treatment of the host cell. Conversely, although MAb 1209-C2 also reacted moderately with PTK and TC cells, pre-treatment of these cell cultures with the MAb did not inhibit invasion by either MAB 1209-C2-reactive or -nonreactive parasites. Collectively, the data indicated that refractile body antigens of sporozoites of Eimeria and Caryospora, which are recognized by MAb 1209-C2, may function in cellular invasion, but also suggest that cellular invasion is probably not mediated by interactions between the conserved epitopes in sporozoites and cultured host cells that are recognized by the MAb.

Experimental transmission of Besnoitia caprae in goats.

Experimental transmission of Besnoitia caprae from naturally chronically-infected goats to susceptible ones was achieved by intra-nasal instillation and intra-conjunctival inoculation of cystozoite-containing suspensions, subcutaneous implantation of fascia containing cysts and alternate needle pricking between the infected and non-infected goats. Typical chronic symptoms developed in the fascia-infected does. Cystozoite inoculation into the eyes and mouth did not result in infection. Kids born of dams with acute and chronic besnoitiosis did not contract the infection in utero, suggesting that intra-uterine transmission may not occur. In contrast to does with acute besnoitiosis, which occasionally aborted, the does with chronic besnoitiosis gave birth to healthy kids. Kids below the age of 4 months (pre-weaned period) born of both infected and non-infected does were susceptible to besnoitiosis but appeared to be more resistant than adult goats.

Pathogenicity of experimental caryosporosis.

Pathogenicity of the coccidia C. bigenetica and C. simplex was studied in experimentally inoculated pigs, goat kids (untreated and immunosuppressed) and severe combined immunodeficient (SCID) mice. The major pathological changes of caryosporosis were similar in all inoculated animals. In pigs and goat kids, caryosporosis was self-limiting, with clinical responses that included focal swelling and erythema of the muzzle, snout, jaws, cheeks, eyelids, bases of the ears, backs of the necks, scrotum, external genitalia of females, legs and footpads. Histopathological changes were characterized by involvement of the cutaneous mononuclear phagocyte system with an inflammatory exudate containing numerous macrophages, especially around the root sheaths, sensory nervous corpuscles of the hair follicles and surrounding dermal free nerve endings. The tactile hair follicles in the muzzle, snout and upper jaw were most severely changed. In SCID mice, inoculation with C. bigenetica or C. simplex caused a severe, fatal, systemic disease characterized by dissemination of numerous caryosporan developmental stages into the host mononuclear phagocyte system. This study presents evidence that both caryosporan species tested caused similar clinical signs and lesions of dermal coccidiosis in the mammalian secondary hosts.

Besnoitia sp. (Protozoa:Toxoplasmatinae) from Akodon montensis (Rodentia:Cricetidae) in Santa Catarina State, Brazil.

Tissue cysts of Besnoitia sp. were found in muscles and several organs from a naturally infected Akodon montensis captured in the rural area of the municipality of Timbó, Santa Catarina State, in southern Brazil. Indirect fluorescence and enzyme-linked immunosorbent assays carried out with sera from mice chronically infected with Toxoplasma gondii and Besnoitia sp. showed, as expected, a stronger reaction against homologous than heterologous antigens. No cross-protection was observed in mice immunized with T. gondii when challenged with Besnoitia sp. This is the first description of a natural infection of A. montensis by parasites of the genus Besnoitia sp. in Brazil.

Differentiating between Besnoitia besnoiti from cattle and Sarcocystis hoarensis from rodents.

To provide a biological basis for studies designed to establish the mode of transmission of the veterinary pathogen Besnoitia besnoiti, we compared salient features of this pathogen in cattle with those of Sarcocystis hoarensis in rodents. The cysts and cystozoites of these organisms can readily be distinguished morphologically. In contrast to S. hoarensis, which is well adapted to rodents, B. besnoiti fails to mature in jirds or mice and generally is lethal in jirds. Serological reagents discriminately detect these pathogens. B. besnoiti, therefore, can unambiguously be differentiated from S. hoarensis either by morphological or serological methods or on the basis of experimental comparisons of virulence in laboratory rodents.

The route of immunization of gerbils with live Besnoitia besnoiti as a factor in protection against lethal challenge.

Gerbils (Meriones tristrami) were infected subcutaneously or intraperitoneally with live culture-grown Besnoitia besnoiti at doses ranging from 10(1) to 10(7) endozoites. All animals injected subcutaneously survived the infection and were refractory to a lethal challenge dose of 10(7) endozoites given intraperitoneally 6 weeks later. By contrast, gerbils surviving primary intraperitoneal inoculation with 10(2) to 10(6) endozoites showed a variable survival rate to challenge. All gerbils developed antibodies to B. besnoiti regardless of the route of inoculation, except for those given 10(1) endozoites intraperitoneally. There was no statistical difference between the immunofluorescent antibody titres developed in groups vaccinated subcutaneously or intraperitoneally (P = 0.556).

Preliminary findings from an experimental study of caprine besnoitiosis in Kenya.

Inoculation of cystozoites obtained from natural, chronic cases of caprine besnoitiosis produced clinical disease in goats but not in rabbits, mice, guinea pigs, hamsters, rats or cattle. Histological examination of tissue sections from the experimental animals showed Besnoitia cysts only in goats. This, together with field observations that cattle reared together with goats having besnoitiosis do not contract the disease, suggests that the Besnoitia species that infects goats in Kenya is host-specific and is not Besnoitia besnoiti. We suggest that the name Besnoitia caprae be adopted for the caprine pathogen.