BARI/ITALY, July 19th (BIERMANN) – Previous field studies were able to show that temperature is the most important factor driving population dynamics of Rhipicephalus sanguineus (Acari: Ixodidae), also known as brown dog tick. This is why Dr. Filipe Dantas-Torres from the Department of Public Health and Animal Breeding at the Università degli Studi di Bari in Italy and his colleagues studied the effects of prolonged exposure to low temperature on eggs of the brown dog tick. They established nine groups (II-X) with five eggs each that were maintained at 8 ± 2 °C (70 ± 10% RH, and scotophase) for 15, 30, 45, 60, 75, 90, 105, 120, and 135 days. A control group (I) was kept in the incubator (26 ± 1 °C, 70 ± 10% RH, and scotophase).

The mean egg incubation period from group I was 11.6 ± 0.5 days. The egg hatch rate was 99.5 ± 0.5 percent. Conversely, no eggs hatched at 8 °C, the authors write. The temperature correlated with the incubation period (r= 0.44), egg hatch rate (r=-0.95) and larval longevity (r=-0,99).

The results show that with declining temperature, eggs of the brown dog ticks are unlikely to hatch and if they actually do so, larval survival is reduced.  Thus, establishing population in cold climate countries is difficult for this species. Conversely, increasing temperature contributes to its propagation.

References

• Vet Parasit 171(3-4):327-330