Necrobacillosis in Springbok
NECROBACILLOSIS IN SPRINGBOK (Antidorcas marsupialis marsupialis)
E. Lane, I. Espie, L. Venter, M. Henton
Between August 2004 and January 2005, 3 female and 1 male adult Springbok at the National Zoological Gardens in Pretoria died suddenly. The females were either pregnant and/or lactating.
Necropsy examination of the first case revealed a severely inflamed oral cavity, with impaction of food in the mouth. Many fine filamentous bacteria were associated with necrosis of the oral mucosa. The nasal sinuses were inflamed due to the presence of food material in the nose. The second case had many ulcers in the rumen, which were associated with sharply demarcated, white, dry, crumbly abscesses containing fine filamentous bacteria in the wall of the rumen, as well as in the liver, spleen, kidney, and peritoneal surface of the body wall. Adhesions between the affected organs and adjacent tissues were prominent. The liver had ruptured and caused extensive bleeding into the abdominal cavity. Fusobacterium necrophorum was isolated from the liver abscesses. Cases 3 and 4 also had ulcers and abscesses in the rumen wall, as well as in the body of the base of the tongue. Arcanobacterium pyogenes and a Bacteroides spp were isolated from the tongue.
Three of the Springbok had lesions consistent with oral necrobacillosis, caused by F. necrophorum. In domestic calves the disease is found in conditions of suboptimal hygiene, where calves are closely confined, and where roughage or foreign material in the hay or bedding results in damage to the oral mucosa. Cases have been found in Boer goat kids feeding on thorny shrubs. Two Springboks had liver abscesses, which in domestic cattle are associated with inflammation of the rumen caused by many bacteria, including those isolated in these cases (F. necrophorum, A. pyogenes and Bacteroides spp). Development of rumen inflammation is thought to be triggered by factors such as feeding a diet low in fibre, but high in easily fermentable carbohydrate; ingestion of sharp foreign objects from the pastures; and the presence of wet climatic and soil conditions. Fusobacterium is a fine filamentous anaerobic bacterium that is present in the mouth, upper respiratory, gastrointestinal and urinary tracts of normal cattle, sheep and goats. Under crowded, wet, unhygienic conditions it can therefore be present in high concentrations in the soil. It does not normally penetrate the walls of these tracts or cause inflammation. However, co-infection with A. pyogenes can, under certain conditions, allow Fusobacterium to become pathogenic.
No further cases have been seen to date, thanks to control measures put in place by the National Zoological Gardens. These include the practice of strict hygienic measures including removal of faeces; and feeding of better quality hay as the season progressed. The damage done to the gastro-intestinal tract likely occurred while the springbok were being fed inferior quality hay in late winter. Additional control measures could include reducing the levels of cubes in the diet, removal of any sharp foreign objects from the enclosures, and drainage of wet areas. In domestic livestock, vaccination against Fusobacterium is useful, and rumen abscesses are less frequent in cattle to whose diet calcium carbonate has been added.
In summary, then, this case series verifies that necrobacillosis occurs in springbok. It is to our knowledge the first record of the susceptibility of springbok to this disease. Interestingly, an outbreak of lameness due to Fusobacterium related foot disease in gemsbok in Namibia, did not affect springbok sharing the habitat. But it appears that captive springbok are particularly susceptible to oral and ruminal necrobacillosis, considering that no other ruminants presented with similar lesions during the same time period. Free-ranging springbok feed on the shoots and leaves of sprouting grasses, shrubs and trees – food that is of high nutritional value – and are highly selective feeders. This selective ability may not be possible in the restricted diets offered to them in captivity, a factor that may contribute to their susceptibility to necrobacillosis. It may also be relevant that the three females were pregnant and/or lactating, which would have increased their nutritional requirements and possibly increased their susceptibility to disease. In addition, it appears that the predisposing factors and, therefore, possible control factors in springbok are similar to those in domestic livestock. These cases emphasize the importance of ensuring that captive animals are fed food of the highest possible quality.
We would like to acknowledge the continued support of the National Zoological Gardens, and its commitment to a pathology monitoring programme, which facilitated the identification of this important case series. We thank the organisers of this PAAZAB meeting for the opportunity to present these findings at its 16th annual conference.