Resistance of calves to Cryptosporidium parvum: effects of age and previous exposure

Abstract

Cryptosporidium parvum is a coccidian parasite that causes diarrheal disease in many vertebrate species, including young (less than or equal to 1 month old) calves. Older calves and adult cattle are resistant to infection. In this study, newborn calves were raised in isolation from C. parvum for 1 week to 3 months before experimental challenge with the parasite. Calves orally challenged with C. parvum at 1 week of age shed oocysts in their feces and had diarrhea after challenge exposure. When these calves were rechallenged at 1 and 3 months of age, they neither shed oocysts nor had diarrhea. There was no significant increase in the mean anticryptosporidium enzyme-linked immunosorbent assay serum antibody titer in these calves following any of the challenge exposures. Calves orally inoculated with C. parvum for the first time at 1 month of age shed oocysts, had diarrhea after challenge exposure, and were resistant to rechallenge at 3 months of age. These calves had a twofold increase in serum antibody titer after the first challenge and no increase after the second challenge. Calves orally inoculated with C. parvum for the first time at 3 months of age shed oocysts, and two of seven animals had diarrhea. These calves had a 10-fold increase in serum antibody to C. parvum after exposure. This study demonstrates that calves raised in isolation from C. parvum remain susceptible to challenge until at least 3 months of age. Furthermore, within this time period, initial exposure and recovery renders calves resistant to further challenge with the parasite. The data also suggest that exposure of young calves to C. parvum may inhibit the development of a serum antibody response to the parasite.

Pathophysiology of Diarrhea in Calves

“…However, diarrhea caused by C parvum rarely occurs after 3 months of age. [57][58][59][60][61][62][63] After infection, clinical signs peak at 3 to 5 days and last 4 to 17 days. 60,64 Some studies have shown that up to 100% of dairy calves become infected with C parvum, 58,65 and become the major source of environmental contamination because calves shed up to 10 7 oocysts per gram of feces.…”

“…59,66 Calves appear to be resistant to subsequent infection after the initial episode of C parvum diarrhea. 63 Severity of diarrhea and incidence of clinical signs in calves shedding oocysts can be variable within and between farms, leading some to question the true importance of C parvum as a primary pathogen; 67 however, it has been repeatedly isolated independent of other known pathogens in clinical cases. 57…”

Cryptosporidium parvum infection in cattle: are current perceptions accurate?

“…Adult beef and dairy cattle also pose little risk with respect to zoonotic transmission of C. parvum as infections are extremely rare. Following infection, calves develop lasting immunity to C. parvum and are resistant to secondary challenge [26]. Thus, the high prevalence of the parasite amongst young dairy calves combined with the development of immunity, probably accounts for the low prevalence of C. parvum in adult dairy cows.…”

A review of the importance of cryptosporidiosis in farm animals

“…In practice, oocyst excretion has been described as early as 3 days of age, which means that calves are already susceptible for infection during or shortly after birth [37±39]. Calves raised in isolation from Cryptosporidium remain susceptible to infection at older age, but the clinical signs become less severe [40]. In neonates, a great variability was observed in the severity and duration of diarrhoea due to cryptosporidiosis, even when the animals were exposed to similar conditions.…”