Molecular survey of Bartonella spp. and Ehrlichia canis from sampled ticks of small ruminants in Kurdistan province, Western Iran

Ticks are small, blood-sucking arachnids that act as mobile delivery systems for a wide variety of microscopic germs. While many people know them for spreading diseases like Lyme disease, they carry other bacteria that are less famous but equally capable of moving between animals and humans. Two such groups of bacteria are Ehrlichia and Bartonella. Ehrlichia bacteria live inside the cells of their hosts and can cause fever and fatigue in both people and animals, while Bartonella species are known for causing a range of illnesses, from mild fevers to more serious heart and nerve conditions. Because these germs travel on ticks, understanding which ticks carry them and where they are found is essential for protecting the health of livestock and the people who live near them. In regions where sheep and goats are raised, these animals often serve as a bridge, carrying ticks that might eventually bite humans.

In the rugged, mountainous landscape of Kurdistan Province in western Iran, a team of researchers set out to map the presence of these specific bacteria in the ticks attached to small ruminants. The province is a major center for sheep and goat farming, making it a critical area to study for potential disease risks. Between June and August 2024, the scientists visited eight different counties across the region, examining nearly four hundred sheep and goats from thirty-nine separate herds. They carefully collected every tick they found from the animals' ears, udders, and the area around the tail, preserving them for laboratory analysis. In total, they gathered five hundred and nineteen ticks, a diverse collection that included six different species. The most common were two types of Rhipicephalus ticks, which made up more than ninety percent of the total, while the remaining few belonged to the Hyalomma and Dermacentor genera.

Once the ticks were back in the lab, the researchers used molecular tools to search for the genetic fingerprints of Ehrlichia canis and Bartonella. This process involved breaking open the ticks to extract their DNA and then using a sensitive test that could detect even tiny amounts of bacterial genetic material. The results revealed a clear, though uneven, picture. The team found DNA from Ehrlichia canis in a small number of tick groups, specifically in six out of the many pools they tested. This means that about one and a half percent of the tick groups carried the bacteria. The infection was not spread evenly across the province; it appeared in four specific counties—Dehgolan, Qorveh, Baneh, and Marivan—and was found mostly in the Rhipicephalus bursa ticks, with a single instance in the Rhipicephalus sanguineus species. This patchy distribution suggests that the bacteria circulates in specific local pockets rather than being a uniform threat across the entire region.

In contrast, the search for Bartonella turned up nothing. Despite testing every sample, the researchers did not find a single trace of Bartonella DNA in any of the ticks. This absence does not necessarily mean the bacteria is completely gone from the area, but it does suggest that if it is present, it is either very rare or exists in such low numbers that the test could not detect it. The study highlights that while Ehrlichia canis is present in the ticks of western Iran, it is circulating at a low level, and the risk of transmission appears to be localized to certain areas and specific tick species. The findings provide a clearer baseline for understanding how these bacteria move through livestock populations, showing that the landscape of disease risk is complex and varies from one valley to the next. This knowledge is a vital first step for local health officials and veterinarians who need to design targeted strategies to monitor and control these invisible threats.