Lanham and Godfrey (1970) with negative results.

No abstract

The significance of Glossina morsitans submorsitans Newst. to the livestock economy of Northern Nigeria is mentioned. Differences in the ecology of the fly have been noted in the Guinea and Sudan savannah zones, respectively. In the former, its distribution is relatively widespread and diffuse, whereas in the latter it is restricted to linear strips associated with river flood plains. The area dealt with in the present work lies in the Sudan zone. The relationship of the fly to its vegetational environment is described, there being a marked concentration of almost the whole tsetse population in evergreen forest islands of relatively limited extent in the second half of the dry season. The source of food is mainly warthog, which were numerous in the area.A focus of the fly, covering an area of seven square miles, in which the dryseason concentration sites, mainly forest islands, amounted to approximately 200 acres, was selected for an experiment. It was isolated from the main focus by a natural barrier five miles wide.Possible eradication measures in this focus are mentioned and reasons given for adopting the application of a residual insecticide.DDT, in the form of a 50 per cent, wettable powder as a 5 per cent, suspension of actual DDT in water, was applied, during the second half of the dry season, at an estimated rate of 20 lb. per acre to the evergreen forest islands, which had previously had paths slashed around and through them. Pneumatic knapsack sprayers were used. A preliminary trial showed that, for up to six weeks after application of the insecticide, examples of G. morsitans from unsprayed forest, placed in contact with sprayed leaves and bark, died in three hours, controls remaining alive for 24 hours. It is suggested that this good persistence may be attributable to the fact that the treated surfaces were in the shade, and that the application was made during the rainless season and at a time when the vegetation was dormant. There was a rapid decline in the population of G. morsitans after spraying. The flies persisted longest (5 weeks) in a site associated with Mitragyna inermis. One application only was given to one part of the focus and in many others one application would probably have sufficed, the second being given in most instances to control G. tachinoides Westw., which was also present, and only in two instances for the eradication of G. morsitans that persisted after the first application. One of these was the site associated with Mitragyna inermis, mentioned above. The last specimen of G. morsitans was caught five weeks after the first application, and none has been caught in the sprayed area for up to 18 months after spraying. The cost of the insecticide and labour to apply it amounted to £700 for an area of seven square miles of focus in which the dryseason concentration sites to which insecticide was applied amounted to approximately 200 acres. The final result regarding G. tachinoides was indefinite for reasons which are mentioned.

SUMMARYA T. vivax infection was syringe passaged in a series of animals and exposed to various levels of treatment with diminazine. The original mixed infections were highly pathogenic but only T. vivax relapsed following treatment at the level of 3-5 mg/kg, and at this stage the infection was less pathogenic than later.Following two additional sub-curative treatments of 1-75 and 3"5 mg/kg, and seven serial passages followed by three successive sub-curative exposures to 10.5 mg/kg, infections were obtained which eventually relapsed to 14 mg/kg.Relapse intervals bore little relationship to the size of the sub-curative dose. They lengthened progressively in the relatively few animals which eventually became only periodically parasitaemic or aparasitaemic. There was no extension beyond 48 hours of the time taken for progressively tolerant infections to become aparasitaemic nor was there any shortening of the relapse intervals following initial treatment of more tolerant infections at lower levels.

An account is given of the simultaneous control of three species of tsetse fly by the selective application of insecticide to vegetation within an area of 16 sq. miles along a seasonal watercourse in Northern Nigeria constituting a permanent habitat of Glossina palpalis (R.-D.) and G. tachinoides Westw. and a hot-season concentration area of G. morsitans Westw. subsp. submorsitans Newst. The ecological zones concerned centred on small lakes fringed, in succession outwards, by open swamp, swamp woodland, swamp forest, riparian forest and riparian woodland, the whole being bounded by savannah woodland populated by G. morsitans in the wet season. All except the forest elements were subject to seasonal fires.Against G. morsitans, insecticide was applied to the principal resting sites of flies in their hot-season concentration habitats, namely, the basal 5 ft. of shaded tree trunks over 9 in. in diameter, or 5 in. where stands were dense, in, chiefly, riparian woodland and forest. Against the other species it was applied to a height of 2½ ft. on stems, trunks and exposed roots in riparian forest and the margins of swamp forest, which were favoured as pupation sites and in which it was therefore believed that adults might rest.A wettable-powder suspension containing 3¾ per cent. DDT was applied by pneumatic knapsack sprayer in quantities short of run-off. Temporary reduction of the strength to 2½ per cent, had no detectable effect on control.Regular fly patrols showed an initial reduction in apparent density of G. morsitans by four-fifths, but spot checks detected a residual population that persisted up to two months in small areas. These were resprayed so as to include trunks of 5 in. diameter and branches over 3 in. in diameter at heights of 6–12 ft. The apparent density of the other species declined after treatment by over nine-tenths, in both treated and untreated zones, but following catches of a few teneral adults, indicating persistent or recurrent populations in limited areas, these were resprayed using an emulsion containing 3¾ per cent, dieldrin.Treatment began in January 1961 and to date (April 1963) no fly has been detected since April 1961, despite repeated re-surveys. The approximate cost of labour, equipment and insecticide was £3,000; an attempt at reclamation in 1926–29 by sheer-felling over seven sq. miles, which achieved only temporary success, had cost £3,000, with recurrent annual re-slashing costs of £250, equivalent to £12,000 and £1,500, respectively, at present-day costs for labour.