Natural Heterobilharzia americana infection in horses in Texas.

The researchers conducted a study to identify the prevalence of Heterobilharzia americana infection in horses in Texas. They found that out of 12 horses with hepatic granulomas, DNA from samples showed 8 were indeed affected by this parasite while for the remaining the primary clinical disease was not Heterobilharzia americana infection.

Research Details

• The schistosome Heterobilharzia americana is a parasite that typically infects dogs, raccoons, and other mammals in the southeastern United States. The migration of its eggs into the mammal’s liver can cause formation of parasitic granulomas accompanied by varying degrees of fibrosis and inflammation.
• Researchers were interested by recent findings that showed these parasitic granulomas in horses were also caused by H. americana infections. Thus, they undertook the current study to understand the prevalence and impact of these infections on horses.

Methodology

• They performed an autopsy or surgical biopsy on 12 horses that had hepatic granulomas. These selected horses were either known to or suspected to have been affected by the H. americana infection.
• Liver samples were taken from these horses and were then used for DNA extraction. The researchers used polymerase chain reaction (PCR) amplification and sequencing with primers specific for a portion of the H. americana small subunit ribosomal RNA gene.

Results

• The researchers expected to produce a PCR amplicon of a specific size from the extracted DNA if a H. americana infection was indeed present. This was the case in 8 out of the 11 horses, suggesting a strong presence of the infection in these animals.
• Sequencing of the amplicons from 5 out of the 8 positive horses indicated a 100% identity with H. americana, thereby confirming the infection.
• In the majority of the cases (10 out of 12), Heterobilharzia was not the primary cause for the clinical disease highlighted, i.e., the hepatic granulomas in these horses were incidental findings unrelated to the main health issues of the animals.

Conclusion

• This study highlights the prevalence of Heterobilharzia americana infection in horses, and its potential as a cause for hepatic granulomas. However, it also interestingly suggests that in many of these cases, the granulomas might not be directly related to the primary health issues of the horses.