An investigation of the cause of enteritis in ostrich (Struthio camelus) chicks in the Western Cape Province, South Africa

Abstract

Ostrich (Struthio camelus) chicks less than three months of age are observed to experience a high mortality rate of 30-40% that is often associated with enteritis. In the event of a disease outbreak mortality can reach 80-100%. Morbidity in those individuals that survive an episode of enteritis, leads to poor growth rate. Enteritis is a multifactorial syndrome that is seen in different animal species. Various infectious agents have been mentioned in relation to the syndrome but no clear cause of the condition has yet been identified. Clostridium perfringens especially in broiler chickens is recognised as a cause of necrotic enteritis. Salmonella spp. and Escherichia coli are recognised factors of enteritis in chickens and turkeys, where damage to the intestinal mucosa has occurred as a result of a co-existing viral infection. This study was undertaken to investigate different infectious agents implicated in enteritis in ostrich chicks. Post mortems were performed on 122 ostrich chicks aged from one day to three months of age. Small and large intestines were kept on ice or at 4°C for bacterial culture and collected in 10% formalin for histopathological examination. Fresh intestinal contents were collected for electron microscopy and rectal faeces collected for faecal flotation test for helminthic or coccidial eggs and staining by safranin counterstained with methylene blue to detect Cryptosporidium oocysts. Escherichia coli (49%) was the most frequently isolated from the samples followed by C. perfringens (20%), Enterococcus spp. (16%) and Salmonella spp. (7%). Eight percent was made up of other less significant bacteria and samples where no bacteria were isolated. Of the E. coli, 39% were categorised as enteropathogenic E. coli, 4% enterotoxigenic E. coli and no enterohaemmorrhagic E. coli were found. For the purposes of this study, those E. coli that could not be categorised were considered as non-pathogenic. The majority (93%) of C. perfringens were type A and only 7% were type E. Clostridium perfringens type B, C and D were not present. The netB toxin gene was identified from 16% of the C. perfringens. All the C. perfringens type E harboured the netB toxin gene and just 10% of the C. perfringens type A had this gene. Three Salmonella serotypes were identified, S. Muenchen (80%), S. Hayindongo (13%) and S. Othmarschen (7%). Necrotic enteritis, non-specific necrosis and sloughing lesions of the intestines were identified. Different bacteria mainly; E. coli, C. perfringens and Salmonella spp. were isolated in association with these lesions. Eight enteroviruses or enterovirus-like particles, one reovirus, one birnavirus and one unidentified viral particles were identified from 76 samples. No helminths, no coccidia and no Cryptosporidia were identified from the samples.