Isolation and primary infections in goat kids of an Eimeria christenseni field strain (Canary Islands)

Abstract

Caprine coccidiosis is a disease that produces gastrointestinal damage and important economic repercussions due to the decreased weight gain and deaths of infected goat kids. It is caused by the protozoan Eimeria, however, not all the species are in the same scale of pathogenicity. This study provides information about the isolation of a field Eimeria christenseni strain, its morphological characteristics and infectivity, development and clinical effects upon experimental infections in goat kids. Faecal samples from naturally infected goats and high percentage of E. christenseni (> 90 %) were collected from a local farm located in Gran Canaria (Canary Islands, Spain) and used to infect 3 donor goat kids under experimentally conditions, aiming to amplify oocyst production and achieve higher purity of E. christenseni oocysts. Morphological characteristics of the excreted oocysts were microscopically analysed by measuring 200 oocysts and 200 sporocysts. Furthermore, isolated oocysts were used to experimentally infect two weeks old goat kids. A total of 2 x 105 sporulated oocysts per animal were used for infections. Upon infection, oocysts shedding, clinical signs and productive parameters were monitored for 4 consecutive weeks. Uninfected goat kids served as control animals. The oocysts released from the isolated E. christenseni strain were a mean size of 40.46 x 27.30 µm, bigger than other Eimeria spp., they had an oval shape and presented a micropillar cap of 2 µm thickness. Results showed that the strain had a prepatent period of 14-15 days and a patent period of at least 28 days post infection. The production of oocysts was very high, with maximum levels at day 25 p.i., where mean values of about 6 million oocyst per gram of faeces were found. Despite high oocyst release, no clinical signs or significant changes on weight gain could be observed, suggesting that the strain isolated here is of low pathogenicity. Further studies are needed to clarify the immunological mechanisms underlying caprine coccidiosis to explain why Eimeria species with similar life cycles such as E. christenseni and E. ninakohlyakimovae are different in terms of pathogenicity.