Infectivity of Cryptosporidium parvum genotype I in conventionally reared piglets and lambs

Abstract

Parasites of the genus Cryptosporidium are intracellular parasites that occur throughout the animal kingdom and have been reported in many species of mammals, including human. Most infections in humans are caused by two C. parvum genotypes, genotype I and genotype II; these are the human and the bovine (zoonotic) genotypes, respectively.Successful experimental infection of Cryptosporidium parvum genotype I ''human genotype'' is described in four conventionally reared piglets and in a lamb. The inoculum was originally obtained from two diarrheic children, and the Cryptosporidium genotypes were determined by PCR and rDNA sequencing. The infective dose was between 10 6 and 2·10 6 oocysts. No clinical signs were observed in the infected animals, except in a piglet that showed watery diarrhea. The oocyst shedding period in positive animals ranged between 4 and 10 days. Histopathologic examination of the gastrointestinal tract of two positive piglets revealed shortening of the villi and denudation of the villous tips of the jejunum. In one piglet, the colon mucosa revealed numerous Cryptosporidium oocysts. The storage time of the inocula ( £ 3 weeks in PBS at 4°C) and the age of the animal (newborn) were important for the successful induction of infection.

Sheep May Not Be an Important Zoonotic Reservoir forCryptosporidiumandGiardiaParasites

“…This is the first report, to our knowledge, of a natural C. hominis infection in sheep, although recently, several groups have shown that lambs can be experimentally infected with C. hominis (2,11,17). Cryptosporidium hominis is the only Cryptosporidium species/genotype detected in the present study that is known to regularly infect humans (42) and as only one isolate was identified, this indicates that the public health risk from contamination of catchment areas, effluent and also abattoirs is probably low.…”

Cryptosporidium Taxonomy: Recent Advances and Implications for Public Health

“…Even though the lack of ability to infect mice and goats in cross-transmission studies was used as evidence for the separation of C. andersoni from C. muris (111), thus far it has been difficult to infect cattle of different ages and breeds with C. andersoni of bovine origin (9). The earlier conclusion that C. hominis does not infect experimental animals such as mice, calves, lambs, and pigs is apparently premature, since recent studies have clearly shown that calves, lambs, and piglets can be infected with C. hominis (3,55). "Genotype switching" (a different genotype of oocysts obtained after inoculation with one genotype of oocysts) has also been observed in cross-transmission studies (63,244).…”

“…Unlike C. parvum, C. hominis is traditionally considered noninfective for mice, rats, cats, dogs, and cattle (73,146,185,241,242). However, more recently, C. hominis has been reported from a dugong and a lamb, and calves, lambs, and piglets can also be infected experimentally with at least some C. hominis isolates at high doses (3,55,73,142). Pathogenicity studies with gnotobiotic pigs have shown the prepatent period to be longer than for C. parvum (8.8 and 5.4 days, respectively) and have also shown differences in parasite-associated lesion distribution and intensity of infection (146,186).…”

“…Indeed, C. hominis has been identified recently in a few animals, such as a dugong and a sheep (73,142). Lambs, calves, and gnotobiotic pigs have also been successfully infected with some isolates of C. hominis (3,55,73,186). Recently, some wetland mammals such as beavers and muskrats have been identified as reservoir hosts for Giardia intestinalis and Enterocytozoon bieneusi infections in humans by genetic analysis (207,208).…”

Infectivity of Cryptosporidium hominis and Cryptosporidium parvum Genotype 2 Isolates in Immunosuppressed Mongolian Gerbils

“…The subdivision of C. parvum into two species, C. hominis and C. parvum, has recently been proposed to replace the type 1 and 2 subspecies designations, respectively (23). C. hominis is considered as not naturally infective for animals with few exceptions and, experimentally, some C. hominis isolates were infective at high doses for calves, lambs, and piglets but not for cats, dogs, and rodents, with some exceptions (3,8,12,13,14,22,23,27,32,36). To our knowledge, the present findings represent the first report of reproducible and stable experimental C. hominis infection in the Mongolian rodent gerbil.…”