Organ culture of Rhipicephalus appendiculatus with maturation of Theileria parva in tick salivary glands in vitro.

A technique is described for the organ culture of Rhipicephalus appendiculatus ticks. Whole, unfed adult ticks with the dorsal integument removed, known as backless tick explants, were cultured in enriched Leibovitz' L-15 medium in which they remained active for at least 32 days at 28 degrees C and 9 days at 36 degrees C. Development of Theileria parva, as demonstrated by methyl green-pyronin staining, occurred in the salivary glands of infected backless tick explants held for 8 days at 28 degrees C or 3 days at 36 degrees C. Maturation in vitro of T. parva in backless tick explants was compared with that in cultured excised salivary glands. After 3-7 days at 36 degrees C glands from backless tick explants and excised salivary glands showed similar numbers of infected acini per infected tick. However, after 12 days at 28 degrees C backless tick explants showed 20-30 times as many infected acini per infected tick as excised salivary glands, in two experiments. No assessment was made of degree of parasite maturity or infectivity. It was concluded that both organ culture techniques supported development in vitro of the salivary gland stages of T. parva, but the backless tick explant technique was simpler and gave generally better results than culture of excised salivary glands.