The transstadial transmission of Babesia caballi by Rhipicephalus evertsi evertsi.

The research study investigates how the Babesia caballi parasite is transmitted transstadially (from one lifecycle stage to another) by the Rhipicephalus evertsi evertsi tick. The study found that the ticks could transmit the parasite to two different hosts (a donkey and a horse) across different lifecycle stages.

Methods and Procedure

• The study used Rhipicephalus evertsi evertsi larvae which they allowed to feed on the ears of rabbits.
• About a week after larval infestation, unfed, newly moulted nymphae (the second stage in a tick’s life cycle after larvae) were manually removed and used to infest a splenectomized donkey that had an active Babesia caballi infection.
• Engorged nymphae, meaning those that had fed and fully developed, were collected from the donkey. After these nymphae matured into adult ticks, they were placed on a susceptible horse.

Findings and Results

• The horse contracted a B. caballi infection that became detectable 19 days after the ticks were introduced.
• The infection resulted in a very low parasitemia, or the presence of parasites in the blood, which was patent (visible and measureable) for a duration of 10 days.
• The lowest packed cell volume (the volume of red blood cells in the blood) recorded was 16%. This could be an indication of how the horse’s health was affected by the B. caballi infection.

Implications

• This study showed that B. caballi can indeed be transmitted through transstadial transmission. This means that the parasite can survive and be passed on through different stages of the tick’s life cycle, which includes feeding on different host species.
• The results of this study could have significant implications on how we understand, prevent, and manage tick-borne diseases, especially those caused by B. caballi.