Epidemiology of East Coast fever: some effects of temperature on the development of Theileria parva in the tick vector, Rhipicephalus appendiculatus.

The moulting behaviour of nymphal Rhipicephalus appendiculatus from the laboratory colony and 3 field strains from Kenya was greatly influenced by constant temperatures between 18 and 37 degrees C but was not significantly different for the 4 tick strains. Six batches of R. appendiculatus (Muguga laboratory) nymphs which had engorged on cattle parasitaemic with 4 stocks of Theileria parva (Kiambu 4, Kiambu 5, Muguga and Mbita 4) isolated in Kenya were incubated at constant temperatures between 18 and 37 degrees C during their pre-moult and post-moult periods. The Theileria infections in the salivary glands of the resultant adult ticks were assessed by staining with Feulgen's stain. Two stocks (Muguga and Kiambu 5) developed their highest infections in ticks incubated at 28 degrees C while the other two (Kiambu 4 and Mbita 4) developed their highest infections at 23 degrees C. Constant temperatures of 18, 33 and 37 degrees were detrimental to the development of salivary gland infections. Temperature influenced the rate of development and numbers of the earlier Theileria stages in the ticks. Engorged nymphal ticks incubated for 4 days at 37 degrees C during their pre-moult period developed lower infections than ticks exposed at 4 degrees C for 4 days.