Unexpected results from large-scale cryptosporidiosis screening study in calves in Tanzania

Abstract

A study was undertaken to investigate Cryptosporidium infection in crossbreed dairy calves in two districts in Tanzania. A total of 943 fecal samples from 601 dairy calves were included in the study, with calves from both smallholder dairy farms and from large-scale and medium-scale dairy farms. The modified Ziehl-Neelsen (mZN) technique was used to examine 710 samples, and 13 of these were considered to be positive for Cryptosporidium. These 13 samples considered positive by mZN, along with the remaining 233 samples, were analysed by immunofluorescent antibody test (IFAT). Of these 246 samples examined by IFAT, 15 samples, 10 of which were considered positive by mZN, were also examined by the auramine phenol technique, and 5 samples, all of which were considered positive by mZN, were analysed by PCR. The results from the IFAT, auramine phenol and PCR analyses demonstrated that none of the samples contained Cryptosporidium oocysts, indicating that, cryptosporidiosis is currently not a problem in dairy calves in these regions of Tanzania. These unexpected results are discussed with respect to other reports on cryptosporidiosis in calves that suggest that this parasite is a serious calf disease globally, and particularly in relation to studies from Tanzania. We suggest that results from studies of cattle in Tanzania, in which mZN has been used as the sole analytical method, should be treated with caution.

Cryptosporidium Infections in Africa—How Important Is Zoonotic Transmission? A Review of the Evidence

“…Another potential factor of importance for the lack of infection with C. parvum in African cattle is cattle breed (and, correspondingly, could also be relevant for small ruminant livestock). As noted by Chang'a et al (47), most studies on Cryptosporidium in cattle involve Bos taurus breeds, but B. indicus breeds (which often predominate in African farms) may (145) also supports the suggestion that particular breeds may be more susceptible to Cryptosporidium infection, with significantly higher prevalences of infection reported from Mafriwal cattle (Sahiwal × Friesian crosses) and from Jersey × Friesian crosses. In Africa, a study from Zambia (70) considered that the significantly higher prevalence of Cryptosporidium infection in dairy-farm cattle compared with beef calves or "traditionally reared" calves was due to the management factors.…”

“…Many of these studies use modified Ziehl-Neelsen (mZn) for identification; this has low sensitivity and specificity, and does not enable identification of the Cryptosporidium species. Studies using more accurate tests have revealed contrasting results; for example, a study from Tanzania used, in addition to mZn, immunofluorescent antibody testing (IFAT), auramine phenol staining, and molecular methods to investigate calves for Cryptosporidium infection and, using the latter methods, did not detect Cryptosporidium shedding in 943 calf samples, of which over 6% were diarrheic, despite some positive results with mZn (47). The authors suggest that data obtained using mZn should be treated with caution.…”

“…Furthermore, in such animal management systems, exposure to the climate is also likely to be detrimental to transmission, with desiccation and UV exposure also playing a part (see the later section on oocyst survival in the African envirnoment). Indeed, a study from Tanzania (47) in which a notable lack of Cryptosporidium infection was identified among 601 dairy calves from different management systems, small herd size and climatic factors were considered to be important factors that could have reduced the potential for establishment of infection and/or contributed to disease fade out (141). Similar arguments may also be proposed for why C. parvum may be less established in small ruminants in various African countries (142).…”

Occurrence of Giardia and Cryptosporidium in captive chimpanzees (Pan troglodytes), mandrills (Mandrillus sphinx) and wild Zanzibar red colobus monkeys (Procolobus kirkii)

“…Interestingly, this latter study also reports the presence of ‘ Cryptosporidium ‐like particles’ – suggesting that objects with epitopes that cross‐react with the anti‐ Cryptosporidium monoclonal antibody used in DFA may be excreted in low numbers in the faeces of non‐human primates. It might be speculated that in some studies that report high Cryptosporidium prevalence, a misidentification may have occurred; this would not be a unique situation, as such misidentification has previously been proposed regarding Cryptosporidium excretion in cattle in sub‐Saharan Africa . Alternatively, these might indeed by Cryptosporidium oocysts, but the numbers are insufficient for successful molecular confirmation.…”

Helminths and Protozoa of the Gastrointestinal Tract of Ruminants in Tanzania

“…Bovine faecal samples cattle [63][64][65][66][67]. In all these studies young stock were more affected than adults.…”