The development of Blastocrithidia triatomae (Trypanosomatidae) in the reduviid bug Triatoma infestans (Insecta): influence of starvation.

Fifth instars of Triatoma infestans with established Blastocrithidia triatomae infections were dissected after different periods of starvation. After a short starvation period of 30 days, 60% of the total population (2,700,000 flagellates) occurred in the small intestine. Within the following 3 months, the numbers of living flagellates there (epimastigotes, cysts) were reduced by about 70% and the percentage of dead mastigotes increased to 30% of the respective total population. Epimastigotes always dominated (about 90%), followed by cysts and only up to 3% spheromastigotes. These relations were only slightly changed by starvation. In the rectum, at 30-120 days after feeding, the total population of living epimastigotes was reduced by 90% and the percentage of those attached to the rectal wall decreased from 10% to <3%. During this period, the proportion of dead from all epimastigotes increased from 34% to >99%. In the rectum, the percentage of cysts from the total population of living parasites increased from 41% to 88% at 30-60 days after feeding and remained at this percentage and total numbers, showing that especially the early phase of starvation strongly induced the encystment of B. triatomae.