Seasonal abundance of adult ixodid ticks infesting cattle belonging to resource-limited farmers in the north-eastern Free State Province of South Africa.

A study was undertaken to determine the seasonal abundance of the ticks infesting cattle owned by resource-limited farmers in the north-eastern Free State Province of South Africa. Infestations of Boophilus decoloratus Koch, 1844, Rhipicephalus evertsi evertsi Neumann, 1897, Rhipicephalus follis Donitz, 1910, Rhipicephalus gertrudae Feldman-Muhsam, 1960 and Rhipicephalus warburtoni Walker & Horak, 2000, were monitored on cattle of mixed breeds at monthly intervals from May 1998 to April 1999. High tick intensity on the cattle was observed between March and June, with a peak in May to June 1998 for B. decoloratus and R. evertsi evertsi. Few ticks from the other three species were recovered from the cattle. Small peaks in November to December 1998 for R. warburtoni, and in December 1998 for R. follis and R. gertrudae were observed. Following the winter (June to August), numbers of B. decoloratus declined markedly, while those of R. evertsi evertsi and other rhipicephalids increased. These results represent the first published information on ticks of veterinary importance infesting cattle in the north-eastern part of the Free State Province.

Natural attraction of livestock ticks by the leaves of a shrub.

During examination of leaves of different plants on Rusinga Island, Kenya, ticks were commonly found on the leaves of a plant identified as Acalypha fruticosa Forsk. var. villosa Hutch (Euphorbiaceae). Larvae of Rhipicephalus appendiculatus were the predominant ticks encountered, found quiescent on the undersurface of the leaves. Laboratory investigations showed that significant numbers of ticks were attracted by odours from this plant. It was concluded that the leaves of A. fruticosa are attractive to this tick and have potential for use as a trap to control ticks.

Ixodid ticks (Acari: Ixodidae) and livestock production: effect of varying acaricide treatments on ticks and productivity in east coast fever-immunized weaner and dairy cattle.

In a pilot trial to evaluate cost-effective methods of acaricide application, east coast fever-immunized weaner and dairy cattle were subjected to varying tick control regimens. All experimental cattle were maintained under the same extensive system of management. Their monthly tick load, packed cell volumes, incidence of blood protozoans, weight changes, and daily milk production were noted. Apart from Rhipicephalus appendiculatus Neumann, other tick species found in the study site were R. pulchellus Gerstacker, Amblyomma gemma Donitz, Boophilus decoloratus Koch, and A. variegatum F. The control group under a weekly regimen of dipping had fewer ticks than each of the other groups for both weaner and dairy cattle. However, the percentage of increase in weight of the weaner cattle was least for the control group. The milk production of none of the groups was significantly different from that of the control group, although profit per animal for groups maintained under a monthly or six-weekly regimen of acaricide use was highest. The age of the experimental dairy cattle was found not to have any effect on their milk production. It is suggested that with successful immunization against east coast fever, both dairy and weaner cattle may be subjected to reduced dipping or spraying, the level of relaxation being dependent on the tick challenge. However, similar studies should be carried out in as many agroecological zones as possible using different breeds of cattle. Information on the level of acaricide residues in livestock products from different farming systems should also be generated. Only then can a definitive recommendation for a change from the present national intensive dipping policy be made.

Influence of exposure period and management methods on the effectiveness of chickens as predators of ticks infesting cattle.

Experiments undertaken on Rusinga Island, Kenya, indicated that Rhipicephalus appendiculatus (Neumann) was the predominant tick consumed on tick-infested cattle by chickens, followed by Amblyomma variegatum (Fabricius), Boophilus decoloratus (Koch) and Rhipicephalus evertsi evertsi (Neumann). The number of ticks consumed by chickens released with cattle in a 3 h release period was not significantly different from ticks consumed in a 4 h release period. In a free management system, chickens 1-3 months of age consumed more ticks than older ones; in a confined management system however, chickens 4-6 months of age consumed more ticks than younger birds. Although the numbers of ticks consumed by local and exotic breeds of chickens were not significantly different, a period of 8-10 weeks was necessary for the exotic breeds to become behaviorally adapted to tick predation on cattle. Local chickens bred in environments where cattle were absent took a shorter period of 4-6 weeks to adapt. It was concluded that the relatively large number of ticks consumed by each chicken during the 3 or 4 h release period is an indication that a good reduction of ticks on cattle can be achieved through tick predation by chickens. The preponderance of R. appendiculatus over other tick species consumed was a reflection of its relative abundance on cattle on the island rather than a selective preference for tick species.

Laboratory and field observations on anti-tick properties of the plant Gynandropsis gynandra (L.) Brig.

A shrubby plant, abundant in east Kenya, Gynandropsis gynandra (L.) Brig., was shown to exhibit repellent and acaricidal properties to larvae, nymphs and adult Rhipicephalus appendiculatus and Amblyomma variegatum ticks. All stages of ticks avoided the leaves of the plant and a high percentage of the ticks which were continuously exposed to its leaves died; surviving ticks were weak and inactive but regained activity when exposed to fresh air. The effectiveness of the plant's leaves as a repellent and acaricide was most pronounced on nymphs and least pronounced on adults. Field investigations indicated that ticks were not found up to 2-5 m from the plant in areas where the plant was predominant. The potential of using the plant for tick control within an integrated tick management system in the resource-poor farming context in Africa was highlighted.

Studies on naturally acquired immunity to African ticks. II. Observations on cattle exposed to Rhipicephalus appendiculatus under varying periods of repeated infestations.

Groups of Friesian cattle were infested repeatedly with Rhipicephalus appendiculatus at weekly intervals (eight infestations) and at intervals of 3 weeks (seven infestations) and 6 weeks (seven infestations). The engorgement weight of adults, nymphs and larvae decreased significantly initially, from the second infestation, but rose significantly at later infestations. This rise was more dramatic with larval instars than with any other. A new method for quantifying the resistance status of animals was introduced; this method showed that the resistance acquired by cattle during 6-weekly reinfestations was more stable than that acquired by cattle during weekly and 3-weekly reinfestations. The criteria for assessing natural resistance to ticks was reappraised. These are classified into those serving long- and short-term purposes, and those which have direct and indirect effects. Criteria which could serve long- and short-term purposes include a reduced number of engorged ticks, an increased number of dead male and female ticks, a decreased number of ticks which fed above the critical engorgement weight and an increased number which fed within the pre-mating weight and decreased the number of copulations. The criterion of reduced engorgement weight can serve the short-term purpose only. A new manifestation of resistance to ticks, i.e. decreased moulting weights of nymphs and adults, together with the criterion of decreased egg hatchability, were classified as indirect effects because they were manifested after the ticks had dropped off the resistant cattle.

Acaricidal activity of kupetaba, a ground mixture of natural products, against Rhipicephalus appendiculatus.

Eight substances were screened for the purpose of selecting a natural product as an acaricide for use within an integrated tick management system. One substance proved to be effective as an acaricide against all stages of Rhipicephalus appendiculatus and was named 'kupetaba'. It is a ground mixture of dried tobacco leaves (family Solanaceae) and a mineral called 'Magadi soda' which is mined around Lake Magadi in the Rift Valley province of Kenya. Investigation showed that kupetaba is commonly sold in local markets in East, West and Central Africa, where it is used for many purposes. The substance prevented the completion of all feeding phases of the tick, suppressed the oviposition capacity of the engorged ticks and drastically reduced the hatchability of the eggs. Larvae and nymphs were killed within 24 h of the application of the substance on calves' ears, while large numbers of adult ticks were also killed within 2-3 days of application during in vitro experiments. The suitability of the natural product as a local acaricide which resource-poor farmers in Africa can use to replace commercial acaricides within an integrated tick management system is discussed.

Predation on livestock ticks by chickens.

Chickens were shown to be natural predators of ticks. Rhipicephalus appendiculatus were recovered in large numbers from the crops and gizzards of chickens which had scavenged for 30 min-1 h among tick-infested cattle. Other ticks recovered were Amblyomma variegatum and Boophilus decoloratus. The numbers of ticks recovered ranged from 3 to 331, with an average of 81 per chicken. Cattle facilitated the predation of ticks by certain behavioural actions. Chickens also picked up both engorged and unengorged ticks seeded on vegetation, but unengorged ticks were preferred. The possibility of tick predation by chickens forming a viable biological control component in an integrated tick management system in Africa is discussed.

Studies on ticks of veterinary importance in Nigeria: intrinsic factors influencing oviposition and egg-hatch of Amblyomma variegatum under natural conditions.

During the peak of rains of 1983, 1984 and 1985 in the forest zone of Nigeria, female Amblyomma variegatum engorged to various weights were subjected to different experiments for the purpose of observing the intrinsic factors which influence oviposition and egg-hatch under natural conditions. Two types of oviposition patterns were observed. New terms were introduced to quantify the relationships between the daily weight loss and daily number of eggs oviposited by a tick. These terms are "actual mass", "convertible blood mass", "oviposition efficiency" and "mass conversion rate". A major advantage of adopting the "oviposition efficiency" and "mass conversion rate" is that they relate directly to the measure of the metabolic activity utilized by the tick for the process of oviposition. The entity "convertable blood mass" also enables recognition of individual capability in the utilization of blood mass for oviposition. Investigation on the relationship of weight of eggs with sequence of oviposition showed that eggs were heavier when few eggs were laid than when numerous eggs were oviposited. The heaviest eggs were laid towards the end of oviposition. Two types of relationship were found to exit between the sequence of oviposition and the eclosion period of eggs. Adult A. variegatum engorged to more than 2.49 x were affected by immersion in water for longer than 7 days. Such ticks died without ovipositing and the water in which they were submerged became dark-red. Eggs immersed in water for periods ranging from 1-7 days hatched in about the same number of days as control eggs and their viability in terms of percent-hatch was not affected.

The decline of a Glossina morsitans submorsitans belt in the Egbe area of the derived savanna zone, Kwara State, Nigeria.

In the the early 1970s the Egbe area of Nigeria was known to be one of high trypanosomiasis risk, with four Glossina species G. morsitans submorsitans Newstead, G.longipalpis Wiedemann, G.palpalis palpalis Robineau-Desvoidy and G.tachinoides Westwood present. Grazing by Fulani pastoralists used to be short-term and only in the dry season. In recent years these pastoralists have grazed their cattle in the area throughout the year and this has prompted a reappraisal of the tsetse situation. Tsetse populations were sampled for 3 years using hand-net catches from man or an ox and biconical traps. Resident livestock, slaughter cattle and some of the flies were examined for trypanosome infection. Of the four tsetse species previously reported from the area, only the riverine species, G.p.palpalis and G.tachinoides, were encountered during the investigation. None of the 152 G.p.palpalis and 52 G.tachinoides examined was infected with trypanosomes. No infection was detected in 101 slaughtered cattle, 65 live Muturu, twelve goats and two pigs by wet film examination. However, a 14.3% Trypanosoma vivax infection rate was detected by Haematocrit Centrifugation Technique (HCT) examination in twenty-one slaughtered cattle. Increased human activities over the years had destroyed much of the vegetation and depleted the wild-life population to an extent that resulted in the disappearance of G.m.submorsitans and G.longipalpis, resulting in turn in a greatly reduced trypanosomiasis risk. It is likely that a similar trend is occurring in other areas of the Derived Savanna and Forest zones of West Africa as the human population expands.(ABSTRACT TRUNCATED AT 250 WORDS)

Saurian malaria in Kenya: epidemiological features of malarial infections in lizard populations of the West Pokot District.

During investigations into the prevalence of malarial parasites among lizards in the West Pokot District in Kenya, 179 lizards comprising eight species were caught. Examination of the Giemsa-stained smears made from their blood showed that 34 lizards were infected with Plasmodium species. Fifteen lizards were infected with a single species of Plasmodium and 19 carried multiple infections, the maximum, in four lizards, was four species. There were 19 combinations of parasite infections. Seventeen Plasmodium species were identified, the commonest being P. icipeensis. Only two of the eight lizard species were infected: the skink Mabuya striata and the agamid Agama agama. Eight of the Plasmodium species infected both; another eight species infected M. striata only but three of these have been described from different lizard families elsewhere in Africa. P. robinsoni infected A. agama only, although it was first described from another lizard family in another part of Africa. The epidemiological significance of these results is discussed.

Synergistic effect of migrating Ascaris larvae and Escherichia coli in piglets.

The effect of intestinal flora on the establishment, development and pathogenicity of Ascaris suum larvae in piglets (Large White breed) was investigated. The infected piglets with Ascaris and Escherichia coli showed signs of pneumonia, cough with respiratory difficulties initially even though these moderated with time. They lost appetite and showed signs of unthriftiness with loss of weight. The packed cell volume was normal but the differential leucocyte counts of the pigs infected with Ascaris larvae and bacteria had high neutrophils, unlike the very high lymphocyte count observed in piglets with ascarids only. The piglets had generalized serous atrophy of body fat. The pericardial and perirenal fats were gelatinous. There was a firm and nodular grey and red hepatization with abscess pockets in the intermediate and anterior one third of the diaphragmatic lobes of the lungs. The liver contained greyish-white and depressed focus immediately dorsal to the area of attachment to the gall bladder with multifocal areas. There was no significant gross lesion in the control animals. Cultural and microscopic examinations of some internal organs of the infected animals showed that bacteria were carried to the lungs by the migrating Ascaris larvae. The combined synergistic effect of Ascaris larvae and E. coli was also investigated and it was concluded that the two agents (A. suum larvae and E. coli) worked together synergistically.

Effects of Trypanosoma brucei and Babesia microti infections on the primary granulomatous reaction to Schistosoma eggs in mice.

Mouse infection with the blood protozoa Trypanosoma brucei suppressed significantly the frequency and intensity of the primary granulomatous inflammatory response to eggs of the blood flukes Schistosoma mansoni and S. bovis injected into the pulmonary microvasculature. In addition, the dynamics of the cellular infiltrate of the egg granuloma were strongly affected. It is suggested that the modulation of the granulomatous response is a result of impairment of the cell-mediated immunological responsiveness induced by T. brucei. Infection with Babesia microti did not induce similar effects on the granulomatous response.

Bacterial isolation from and transmission by Boophilus decoloratus and Boophilus geigyi.

Bacteria were isolated from the haemolymph of Boophilus decoloratus and Boophilus geigyi which had engorged on trade cattle in Nigeria. All the genera of the bacteria were also isolated from the eggs which they laid although some of them were missing from the larvae which eventually hatched. When clean rabbits were inoculated with some genera of bacteria and clean, laboratory bred larvae of B. decoloratus and B. geigyi fed on them, the same genera of bacteria were subsequently isolated from the haemolymph of the engorged adults, the eggs they produced and the larvae which hatched from them. Staphylococcus pyogenes and Pseudomonas aeruginosa were consistently encountered in the haemolymph, eggs and larvae of both Boophilus species while Proteus mirabilis was additionally consistent in B. geigyi.

Prevalence of Anaplasma marginale, Babesia bigemina and B. bovis in Nigerian cattle using serological methods.

Serum samples collected randomly from 500 cattle from the 10 northern states of Nigeria were tested for antibodies against Anaplasma marginale by indirect fluorescent antibody (IFA), card agglutination (CT) and capillary tube-agglutination (CA) tests. The serum samples were also examined for antibodies to Babesia bigemina and B. bovis by the IFA test only. Of the serum samples tested, 79.4% had antibodies against A. marginale by the IFA test, 40 and 25% in the CT and CA tests, respectively. The IFA test results for B. bigemina and B. bovis were 29.4 and 14.1%, respectively.

Anaplasmosis of small ruminants in Nigeria: incidence and parasite identification through blood smear and latex agglutination test (LAT).

A survey was carried out on the incidence of anaplasmosis in small ruminants at Bodija abattoir, Ibadan. 100 sheep and 200 goats were examined using and comparing two methods-the Giemsa stained blood smear and serodiagnosis by Latex Agglutination Technique. The sheep and goats examined were among those brought from various parts of northern states and some neighbouring countries like Chad, Benin, Niger and Burkina Faso. 27% of the sheep and 17.5% of goats were positive for Anaplasma bodies with blood smear method while 54% of sheep and 61% of goats were sero positive with latex agglutination test (LAT). There seems to be a high incidence of anaplasmosis among sheep and goats probably due to the abundance of its arthropod vectors. The serodiagnostic method showed a high degree of specificity and sensitivity and is useful in field diagnosis.

The response of captive rodents to the migration of Ancylostoma caninum larvae.

The distribution of the larvae of Ancylostoma caninum in tissues of captive wild rodents (Rattus rattus) and the leucocytic and behavioural responses of these rodents were studied after experimental oral infection. There was a wide distribution of larvae in tissues with a preponderance of the larvae in the skeletal muscles of the anterior part of the body in older infection. The rats responded by an elevation of total leucocytes and eosinophils in blood, alternation of locomotory activity and behavioural dominance that may have a correlation with predation and epidemiology of A. caninum in a sylvatic setting.