Prevalence of Cryptosporidium infection and associated risk factors in ruminants in Gauteng Province, South Africa

Abstract

Cryptosporidiosis, an emerging enteropathogenic disease with negative implications for public and livestock health, remains poorly investigated in Africa, necessitating focused epidemiological studies. To determine the prevalence and risk factors associated with Cryptosporidium infections in domesticated ruminants, a longitudinal study was conducted on eight farms in Rust de Winter, Gauteng Province, South Africa. During winter (2022) and summer (2023), 370 faecal samples were collected from cattle (n=146), sheep (n=105), and goats (n=119) kept in extensive and semi- intensive production systems. Microscopic analysis using the gold standard Modified Ziehl Neelsen (MZN) test was employed, followed by screening of the positive samples for Cryptosporidium parvum using quantitative real-time PCR (qPCR). Semi- structured interviews were conducted with the farmers to establish demographic, behavioural and management practices that could pose a risk for Cryptosporidium infection between animals and humans. The microscopic analysis identified Cryptosporidium oocysts in 57 (15.4%) of the 370 faecal samples. However, the qPCR detected Cryptosporidium DNA in only one (1.8%) of the 57 MZN-positive samples, possibly because of low oocyst concentration, below the detection limit of the qPCR, or the presence of Cryptosporidium species other than C. parvum. The Cryptosporidium data from the MZN test revealed that infection was significantly higher (p=0.0133) in summer (19.4%) than in winter (11.6%). No statistically significant differences (p>0.05) in infection were observed between male (16.2%) and female (14.0%) animals and across ruminant species, although cattle (11.6%) tended to have lower infection rates than sheep (20.0%. OR=1.9; p=0.075) and similar infection rates to goats (16.0%; OR=1.16; p=0.695). All interviewed farmers (n=13) were unaware of cryptosporidiosis, highlighting the importance of awareness and training to reduce the potential risk for disease transmission to humans and other animals. Despite the limitations associated with the qPCR method, this research provides valuable insights into the epidemiology of Cryptosporidium infections in ruminants in Gauteng Province. The observed seasonal variation and the need for farmer education underscore the significance of proactive measures to mitigate livestock mortality and prevent the potential spread of infection to humans. Further investigation involving more animal farms and assessment of the occurrence of infections in humans will contribute to better understanding of Cryptosporidium infections. There is also a need to evaluate clinical vs sub-clinical cases on farms with regards to the detection limit of nucleic acid- based methods.