Vector Competence of Five Ixodid Tick Species in Egypt for Borrelia

Document Type : Original Article


Entomology Department, Faculty of Science, Ain Shams University, Abbassia, Cairo. Egypt


Ticks are vectors of several disease agents affecting human and animal health. The ability of ticks to acquire, maintain, and transmit disease agents are factor determining the competence of ticks as vectors of etiologic agents. The present study investigates the ability of five ixodid tick species, Hyalomma dromedarii, H. excavatum, H. impeltatum, H. analoticum and Rhipicephalus annulatus to acquire, transstadially and transovarially maintain and transmit Borrelia sp. isolated from their population in nature to a laboratory animal. Although the five ixodids successfully acquired the borrelial infection by feeding on infected New Zealand rabbits, only four of the ixodids showed the ability to transstadially transfer Borrelia from the Larval-nymphal stage to the adult male, and female. Also, only R. annulatus, H. dromedarii, H. impeltatum succeed in transovarially transferring Borrelia from adult females to their progeny. Rhipicephalus annulatus was the most efficient species in acquiring borrelial infection in the laboratory (69.17%) and in transstadially transferring their natural Borrelia sp. from the infected nymphs to the emerged adult males and females with infection rates of 60 and 80%, respectively All infected females R. annulatus transovarially transmitted their natural Borrelia species to the highest percentage of the unfed larval progeny in each of F1 and F2. This was followed by H. dromedarii and H. impeltatum with 54.58% and 39.17% acquisition infection rates, and transstadially transfer Borrelia to males and females (50, 70%, and 30, 50%), respectively. Infected females of both species transmit Borrelia to the F1 and F2 (100,90%), respectively. No transovarial transmission was observed in H. impeltatum and H. analoticum.   In each tick species, the transmission of Borrelia to uninfected rabbits increased by increasing the number of feeding infected stages per rabbit. Generally, female ticks were more efficient than males and adults than immatures in transmitting borrelial infection.