A Glossina community inhabiting a peridomestic agroecosystem encircling Orie-Orba in the Nsukka area was investigated with unbaited biconical traps for species composition, population characteristics and trypanosome infections. Only Glossina tachinoides Westwood and G. palpalis (Robineau–Desvoidy) were encountered, the former comprising over 99% of all 2877 tsetse caught. G. tachinoldes occurred at a weekly mean apparent density of 8.41 ± 0.98/trap which fluctuated in a manner characterized by decrease in the wet season and increase in the dry season. Traps caught males and females in equal proportions during the wet season but during the dry season males outnumbered females in the monthly trap catches. During either season, the female samples comprised mostly old flies. Pregnancy rate was high during both seasons and abortion was the only reproductive abnormality manifested. The size of mature eggs in utero varied in a manner suggesting the occurrence of nutritional stress during both seasons. Approximately 5% of 347 G. tachuinoides examined for trypanosomes were infected with procyclic trypanosomes only.

These observations, which have formed the basis of further investigations now in progress, are discussed in the light of earlier studies at this location and elsewhere, and in the context of certain peculiarities of intensively cropped agroecosystems.

Only one paper in this Symposium dealt with what might be considered a classical zoonosis, namely that of leishmaniasis in northern Egypt. However, the closely related subject of opportunistic infections of humans by protozoa was also covered by two presentations, which noted the likely increase in the incidence of these types of protozoan diseases with the concomitant increase in the reporting of immunodeficiency diseases. A third factor in the evaluation of potential zoonotic foci is how protozoa cause disease symptoms in different host animals, and this point was addressed in the symposium by reference to the pathogenesis of some coccidia.

Descriptions and morphometrics of the eggs and waxen structures on the nymphs and adults of Orthezia insignis are given. Architecturally, the waxen designs are similar throughout the nymphal instars but vary in the construction details. On the newly hatched (issued) nymphs only structural outlines are visible under a binocular microscope and on older instars, wax secretions become progressively more copious and conspicuous. At adult stage, the greatest amount of wax is used to construct the ovisacs. Reproduction was parthenogenetic and embryogenesis was characterized by three colour changes of the eggs: the white, newly laid eggs successively turn light yellow; bright yellow and then brown before eclosion. The frequency of nymphal issuance was influenced by the relative positions of the egg batches inside the sac. Nymphs hatching from eggs laid late in life, took longer to scramble out of the sac. Evidence deduced from the rate of nymphal issuance and the mean number of light yellow eggs at any given time, suggested that ovulation, embryogenesis and eclosion are probably synchronized biological activities in Orthezia.

Development of nymphs in the laboratory took approx. 42 days and was marked by three stadial stages. Morphometrics of the right metathoracic femurs from dead nymphs and exuviae reliably confirmed a similar developmental pattern in wild population.

Effects of pheromone trap design and trap placement methods were tested for catching males of the peach twig borer Anarsia lineatella (Zeller), in Iraq. Zoecon's pherocon lc trap captured more moths than corrugated plastic delta trap.

Significantly more moths were caught in traps hung at a height of 3.0 m above ground (surface) than at any other level of traps. Although more males were caught in the traps placed in south quadrant of the trees than other quadrants, the analyses showed that there was no significant difference between quadrants at P = 0.05. Response to traps at the interior of the orchard was significantly higher than that to the traps in perimeter orchard.

Sixty-four sorghum accessions were screened for resistance to the grain midge, Contarinia sorghicola Coq., under natural infestation conditions at Tamil Nadu Agricultural University, Coimbatore during 1982. Absolute resistance was not found in any of them. Low grain damage was recorded in PVK 50 (6.61%), PVK 55 (11.58%), AF 28 (17.03%) and DJ 6514 (17.05%) while the susceptible accession, SPV 234 recorded high grain damage (92.72%) in the screening trial. The ovipositional preference studies at insectary revealed significantly reduced grain damage in the resistant accessions. Among them, the lowest damage (8.33%) was recorded in PVK 50 followed by AF 28, DJ 6514 and PVK 55 while the susceptible accession, SPV 234 recorded 21.57% grain damage. In the choice experiments, SPV 234 had 11.22–35.36% more infestation than in the resistant accessions evaluated along with it. Studies on development and biology of the midge revealed that antibiosis is one of the mechanisms of resistance in the lines, PVK 50, DJ 6514, AF 28 and PVK 55.

The breeding sites and biology of Phlebotomus pedifer was investigated in the caves of the old focus of cutaneous leishmaniasis in Mt Elgon, Bungoma District, Kenya. Phlebotomus pedifer was found to rest mainly in the poorly lighted areas of the caves, on the roof, the floor of caves under objects, and in cracks and crevices inside the caves. The flies were also found in abundance in cracks and crevices outside the caves where hyraxes were found to rest. Immature stages of P. pedifer were recovered from wet areas of the floor of the caves. The biology of this species was investigated and the mean duration from egg to adult was 37 days.

The vectors of Leishmania major were investigated in Marigat, Baringo District, Kenya, a focus of both visceral and dermal leishmaniases. These studies resulted in the discovery of the resting sites of Phlebotomus duboscqi, a known vector of L. major, and of alternate principal resting sites of Phlebotomus martini, a known vector of visceral leishmaniasis. Furthermore, Sergentomyia ingrami was incriminated as a possible vector of L. major among susceptible rodents inside burrows. Trapping methods which have resulted in the discovery of the resting sites of these phlebotomine sandflies are presented in this paper.

The activities of mankind which introduce excess nutrients and/or pollutants of various kinds into lakes, streams, estuaries, soils and the air, can, and often do, cause significant changes in aquatic and terrestrial environments world-wide. The pollution problem is critical because of the pressures of increasing populations, industrial growth and intensification of agricultural production. Conflicts of interest arise everywhere as challenges to resource use and natural state (‘beauty’) are turned into public issues.

Ground spraying trials involving a new formulation of synthetic pyrethroid, alphamethrin (OMS 3004, WL 85 871) e.c. 10% were carried out in January 1983 against G. palpalis palpalis in the Bouaflé human trypanosomiasis focus, Ivory Coast. Four dosages were tested in five localities: 12 g of active ingredient (a.i.) per hectare; 24, 36 and 48 g (a.i.)/ha. Each dosage was applied once as a residual spray. The atomiser SOLO PORT 423 was used for spraying and the total area treated was estimated at 20 ha.

The results were evaluated with Challier-Laveissière biconical traps. The knock-down and short term effects of the insecticide were very satisfactory, 96–100% reduction in apparent density of the vector obtained with all the four dosages applied during the first 2 months after treatment.

Three to five months after spraying, more than 98% reduction in apparent density of G. palpalis palpalis was achieved even with the lowest dosage of 12 g (a.i.)/ha. The highest dosages tested did not seem to increase the persistence of the insecticide nor the mortality rate of the vector in the study area.

Due to adverse side effects on man at high dosages during and after treatment, it is recommended that in residual ground spraying, alphamethrin e.c. 10% be applied at a maximum dosage of 12 g (a.i.)/ha and at a concentration not exceeding 0.016% of active ingredient.

Piper guineense Schum and Thonn, mixed with cowpea seeds, Vigna unguiculata (L.) Walp, was significantly superior (P < 0.05) to the large, red and mild Capsicum annum var connoides (Miller) and the small, red and pungent Capsicum frutescens L. in causing up to 96% mortality to adults of Callosobruchus maculatus F. within 48 hr. When applied as ground pepper, P. guineense was more active insecticidally than when applied as whole fruits.

Adult bruchids in contact with P. guineense showed significant reduction (P < 0.05) in the numbers of eggs laid, and in the numbers of F1, offspring that emerged compared with adult bruchids exposed to the same doses of C. annum or C. frutescens respectively.

Neither of the peppers reduced the viability of the cowpea seeds or the absorption of water needed to soften the seed testa for decortication before cooking or processing.

At a cost price of U.S.A. $0.003 per 1 g of black pepper, and an effective application rate of 1 g black pepper to 20 g cowpea, there is a saving of over $750 by disinfesting a ton of cowpea with black pepper for a storage period of 2–3 months in a metallic drum which costs less than $50.00

Simultaneously or selectively, nymphs and adults of Orthezia insignis used physiological age of the host-units, the relative sizes of sap pathways and the concentration of photosynthates to choose feeding and/or oviposition sites, depending on the state of the host plant. On the non-flowering plants, physiological age and relative sizes of pathways were the principal determinants, while on flowering food plants all the three criteria were used although the sink-photosynthate-concentration factor had a decidedly dominant influence on Orthezia than otherwise.

The paper analyses the extent to which ticks and tick-borne diseases, particularly East Coast Fever (ECF), are an economic problem in Kenya. It qualitatively argues that several socio-economic factors, viz. inadequate information, indivisibility of the main tick control facilities, externalities, and risk make individual farmers undertake less control efforts than is optimal for the society. This fact is used to justify a more active role for the state in tick control efforts. A simple regression model that tests the impact of ECF on the cattle breed portfolio in the country is presented.

The cotton whitefly, Bemisia tabaci (Genn.), is parasitized by four Aphelinid species: Eretmocerus diversiciliatus Silv., E. mundus Merc., Encarsia lutea Masi. and an unidentified Encarsia sp Whitefly adults move from field weeds onto cotton during the period September–November. The application of broad-spectrum insecticides to control other cotton pests early in the season prevents the establishment of the host-stage of B. tabaci needed by the parasitoids within cotton fields during September and October. The rate of parasitism is consequently decelerated to peak in January towards the end of the season. Peak per cent parasitism for treated cotton fields was 36.7 as compared to 76.8 in untreated fields. This has promoted B. tabaci to an all season pest instead of an early and mid-season occasional pest. Alternative control strategies for early season pests are discussed.

Four groups of scientists were invited to participate in this Symposium, including those who have systematically studied or are still studying the relatively new problems of protozoal viruses of protozoa as inactivators of viruses and on protozoa as potential reservoirs of mammalian viruses would have presented itself.

Unfortunately, not all of the invited scientists could come to Nairobi. The most recent results of the Spanish group on protozoa as inactivators of viruses were not discussed (but see Programme and Abstracts of the Congress).

Ground spraying trials involving three synthetic pyrethroids: OMS 2012 (BAY FCR 1272, cyfluthrin) w.p. 10%, OMS 2013 (BAY NAK 1654, fenfluthrin) w.p. 5%, OMS 3004 (WL 85871, alphamethrin) w.p. 5%, were carried out in January 1984 against G. palpalis palpalis and G. tachinoides in the Bouaflé human trypanosomiasis focus, Ivory Coast. Two dosages of each formulation were tested as residual spray: 12 g of active ingredient (a.i.) per hectare at a concentration of 0.016% and 48 g (a.i.)/ha at 0.064%, The insecticide was applied by means of the atomiser SOLO PORT 423 and the total area treated was estimated at 29 ha. The results were evaluated during 5 months with Challier—Laveissière biconical traps.

OMS 2013 w.p. 5% at 12 g (a.i.)/ha, had unsatisfactory effect on G. palpalis palpalis and G. tachinoides from the first month after spray. At 48 g (a.i.)/ha this formulation showed a moderate effect on both vectors during the first 3 months after treatment, rate of reduction in apparent density by trapping (A.D.T.) varying between 70 and 90%.

OMS 2012 w.p. 10% at 48 g (a.i.)/ha gave satisfactory results, 92% reduction in A.D.T. of G. p. palpalis during the first 3 months after treatment. OMS 2012 w.p. 10% at 12 g (a.i.)/ha gave 94% reduction in A.D.T. of G. tachinoides during the first 2 months after treatment. At the dosage of 48 g (a.i.)/ha, 97% reduction in A.D.T. of G. tachinoides was recorded through the evaluation period.

OMS 3004 w.p. 5% at 12 g (a.i.)/ha, gave 97% reduction in A.D.T. of G. palpalis palpalis during the first 3 months after treatment. At 48 g (a.i.)/ha, 91–98% reduction in apparent density of G. p. palpalis was achieved during the period of evaluation. The effect of this formulation at 12 g (a.i.)/ha on G. tachinoides, was very pronounced during the first 3 months after treatment, being 99% reduction in A.D.T. At 48 g (a.i.)/ha, 100% reduction was obtained during the first 4 months and more than 99% reduction in 5 months after spray.

Laboratory-reared Xenopsylla brasiliensis and X. cheopis obtained from several parts of Tanzania were tested with 0.5% malathion, using the standard WHO test kit.

Two strains of Xenopsylla brasiliensis (Mbulu and Amani) were more susceptible as 100% mortality was obtained after 12 hr exposure. With the remaining populations, 100% mortality was obtained after 24 hr exposure. LT50 of X. brasiliensis were 3.1, 3.3 and 4.5 hr for Mbulu, Tawalani and Amani strains respectively. Similarly, LT50 of X. cheopis were 8.1, 7 and 5.4 hr for Chunya, Amani and Tawalani strains respectively.

It was generally concluded that malathion was a suitable insecticide for use in flea and consequently plague control in Tanzania as X. brasiliensis and X. cheopis are the commonest flea vectors of the disease in the country. Moreover, the insecticide is locally available and it has limited toxicity on non-target organisms and little persistence in the environment.

In the field and laboratory, Gossypium arboreum varieties G 27, LD 133 and LD 230 were less preferred by the jassid, Amrasca biguttula biguttula, and the aphid, Aphis gossypii, than G. hirsutum variety, F 414. The arboreum varieties also supported fewer numbers of the two sucking pests than the hirsutum cotton. These varieties proved potentially susceptible to bollworms Earias spp and Pectinophora gossypiella damage in laboratory tests. Interestingly the varieties exhibited considerable degrees of field resistance. In the field, Earias moths showed no preference for any plant part for oviposition among the four cotton varieties. Of the reproductive parts of the cotton plant offered, first and last instar Earias vittella larvae orientated maximally to bud. Nonetheless, the larvae showed no definite pattern of preference for the fruiting structures of the cotton plant. In the laboratory, the four varieties showed non-significant differences in supporting the growth of Earias and Pectinophora larvae. The number of Earias eggs on the four varieties did not vary significantly. The number of fruiting bodies per plant and Earias incidence were unrelated in the four varieties.

An investigation was carried out around animal burrows in Marigat, Baringo District (Kenya) for 6 months to observe host attraction or host preference of phlebotomine sandflies. Six different kinds of caged animals from groups of Rodentia, Aves, Reptilia, Carnivora and Bovis were used. The host preference of Phlebotomus duboscqi, P. martini and Sergentomyia ingrami were distinctive. Most of the Sergentomyia species preferred feeding on reptilian hosts as is indicated in the blood meal analysis. Among the species were opportunistic feeders on hosts which appeared not to be favoured hosts.

Four goats, which had been previously bitten on two different occasions by Glossina morsitans centralis infected with Trypanosoma congolense and subsequently treated on each occasion with the trypanocidal drug diminazene aceturate were each fed upon by six uninfected tsetse. Hypersensitivity reactions developed in the skin of two of the goats within 1 hr after the bite, and reached a maximum intensity over the next 24 hr. In order to determine whether hypersensitive skin reactions could be induced by tsetse saliva alone, six different goats were bitten by uninfected tsetse up to eight times. Only a few small nodular skin reactions were noticed. However, following infection and treatment and another sequence of uninfected tsetse bites, hypersensitive skin reactions did occur in two animals, although the reactions were not as severe as anticipated. The hypersensitivity reactions usually precede but sometimes overlap the chancre reaction elicited by metacyclic trypanosomes transmitted by tsetse.

Three types of human leishmaniases are known to occur in Kenya: visceral leishmaniasis, caused by Leishmania donovani, and cutaneous leishmaniasis caused by L. aethiopica and L. major. Visceral leishmaniasis is the most important of the three in eastern Africa, not only because it is fatal but also because several epidemics have occurred periodically since the disease appeared in the country about 40 years ago resulting in many deaths. L. aethiopica and L. major are chiefly zoonotic and people contract the disease when they wander into areas containing animal reservoirs and infected vectors. Control measures were undertaken against vectors and reservoirs during an epidemic outbreak of kala-azar in Machakos District.