Probing by Glossina morsitans morsitans and transmission of Trypanosoma (Nannomonas) congolense.

Successive probings on nine mice each by 32 Glossina morsitans morsitans infected with Trypanosoma (Nannomonas) congolense resulted in 54% of the mice (156/288) becoming parasitemic. A second trial with 25 surviving infected flies resulted in transmission by probing to 37.3% (84/225) of the host mice. The patterns of transmission were similar in the two trials, with transmission rates in the first and second probings higher than those for feedings to repletion after nine consecutive probings. Infected flies probed significantly more times and required more time to engorge than noninfected flies. Probing transmissions by cyclically infected flies may be important in the spread of trypanosomes in endemic areas, since feeding interruptions can result in transmission to more than one host at each feeding interval.