A retrospective study of equine actinobacillosis cases: 1999-2011.

This retrospective study investigates the presence and impact of Actinobacillus bacteria in horses over a 12-year period, noting its association with diseases like septicemia and respiratory illness in both foals and adults.

Study Background

• Actinobacillus is a type of bacteria often found in a horse’s oral cavity, gastrointestinal tract, and reproductive tract. While it is usually harmless, under certain conditions it can cause disease.
• This study is a retrospective look at Actinobacillus occurrences in horses from 1999 to 2011. It aimed to review the types of Actinobacillus bacteria isolated and the clinical history, signs, and associated pathologies of the affected horses.

Study Sample

• The study observed 99 horses of various age groups, including 43 foals, 4 young adults, 39 adults, 2 aborted fetuses, and 11 horses of unspecified ages.

Bacterial Strains and Disease

• Actinobacillus bacteria were isolated from the horses 111 times on separate occasions. The most common types identified were Actinobacillus equuli subsp. equuli, and hemolytic Actinobacillus spp.
• The bacteria were often associated with conditions like septicemia (blood poisoning) and respiratory disease in both foals and adult horses. Septicemia was associated with embolic nephritis, a form of kidney inflammation, in neonatal and some adult horses.

Predisposing Factors

• Foals are particularly at risk if they have failed to properly absorb antibodies from their mothers’ milk.
• Sometimes other pathogenic bacteria or viral infections were present alongside Actinobacillus, indicating these could be contributing factors to developing disease.

Findings and Suggestions

• However, in many cases, no other infections or predisposing factors were documented, suggesting that Actinobacillus bacteria can act as primary pathogens, causing disease on their own under the right conditions.