Susceptibility of two-week old Lymnaea natalensis to some plant extracts.

The molluscacidal potency of 17 Nigerian plants extracted by the unevaporated crude water (UECW) method was evaluated on two-week old Lymnaea natalensis Krauss. Five extracts were not active but extracts of Balanites aegytiaca, Blighia sapida, Boswellia dalzielii, Cissampelos mucronata, Detarium microcarpum, Kigelia africana, Opilia celtidifolia, Parkia clappertoniana, Polygonum limbatum, Pseudocedrela kotschyi, Nauclea latifolia and Securidaca longipedunculata were molluscacidal. There is potential for their future use in the integrated control of Lymnaea natalensis, as well as other snails. Mortality data for lethal concentration values for all extracts were analysed by use of probit transformation. The upper and lower fiducial limits of the LC50 (P = 0.05) were also determined.

Screening of some Nigerian plants for molluscicidal activity.

Methanolic (MEOH), evaporated crude water (ECW) and unevaporated crude water (UECW) extracts of 25 Nigerian plants, used for different medicinal and domestic purposes were screened for molluscacidal activity on laboratory-reared Lymnaea natalensis Krauss. Seven of the plants were not active; extracts from 18 (72 per cent) of the plants, some of which are renowned fish poisons, had molluscicidal activity. These were Acacia nilotica, Aristolochia albida, Balanites aegyptiaca, Blighia sapida, Boswellia dalzielii, Detarium microcarpum, Gnidia kraussiana, Kigelia africana, Nauclea latifolia, Opilia celtidefolia, Parkia clappertoniana, Polygonum limbatum, Pseudocedrela kotschyi, Sclerocarya birrea, Securidaca longipedunculata, Ximenia americana, Vetiveria nigritana and Ziziphus abyssinica. The LC50 of these extracts were determined. It is strongly recommended that the toxic effects of these extracts against fish, cercariae, snail eggs and mammals be further investigated so as to determine the right concentration, especially for use in fish ponds.

The efficacy of ivermectin against nematode parasites of White Fulani calves.

Ivermectin was evaluated for anthelmintic activity in calves naturally infected with gastrointestinal helminths. Five of 10 calves were treated subcutaneously with ivermectin at 200 micrograms per kg body weight. One-hundred percent efficacy was indicated against adult and immature Haemonchus, Trichostrongylus, Bunostomum phlebotomum and Oesophagostomum radiatum. Adult Cooperia were also completely eliminated, and a 95.5% reduction was obtained for the immature forms; an 88.7% reduction was obtained for Trichuris spp.

Haemoglobin polymorphism and resistance to helminths in Red Sokoto goats.

Haemoglobin variants were studied in a population of 104 Red Sokoto goats of over 1 year of age and in 49 kids. Three haemoglobin variants and 5 phenotypes were detected. The observed proportions of haemoglobin phenotypes in animals over 1 year of age differed from the expected numbers calculated on the basis of genetic equilibrium, while in kids there was good agreement between observed and expected values. There were significant differences in helminth egg counts among haemoglobin phenotypes. The heterozygotes had significantly lower egg counts than homozygotes. It is postulated that the discrepancy in the observed ratios of haemoglobin phenotypes of the older group was probably due to the differential susceptibility to helminth infection.

Observations on epidemiological and clinical aspects of gastrointestinal helminthiasis of sheep in northern Nigeria during the rainy season.

During the rainy season of 1976 severe gastrointestinal helminthiasis was observed in Yankassa sheep grazing unimproved pasture in northern Nigeria. Until mid August high mortality from acute haemonchosis was mainly in lambs. Later, lambs and ewes died from haemonchosis combined with trichostrongylosis but the course of the disease was less rapid. Animals surviving until the end of October showed combined symptoms of chronic haemonchosis and of trichostrongylosis. A rapid turnover rate of adult and developing Haemonchus contortus resulted in a replacement of the blood sucking stages by arrested early fourth stage larvae from mid August onwards. Trichostrongylus spp had a lower turnover rate and only low levels of arrested development occurred, resulting in a gradual build up of Trichostrongylus spp populations during the rainy season. About three or four generations of trichostrongylids developed throughout the rainy season. The first and second generation caused primarily acute haemonchosis, while later generations caused chronic haemonchosis combined with trichostrongylosis.

Evaluation of oxfendazole against natural infections of gastrointestinal nematodes in Nigerian calves.

The efficacy of oxfendazole was tested in naturally infected Sokoto-Gudali calves at a dosage of 2.8 mg per kg. At this dosage level, oxfendazole showed 100 per cent efficacy against adult and immature forms of Haemonchus spp, Trichostrongylus spp, Bunostomum phlebotomum and Oesophagostomum radiatum. Although efficacy of 100 per cent was recorded for the adult form of Cooperia spp, only 48 per cent reduction was recorded for its immature stages. Similarly, a percentage reduction of 75 was recorded for adult Trichuris spp. No larvae hatched out of a seven-day vermiculite culture of faeces collected from the treated calves 24 h after treatment.

The anthelmintic efficacy of oxfendazole and haloxon against arrested Haemonchus contortus larvae in sheep.

In a controlled trial with natural infection of Haemonchus contortus, oxfendazole at 4.53 mg/kg body weight was highly effective against arrested larvae, developmental stages and adult helminths. Haloxon at 40 mg/kg significantly reduced helminth burdens.

Pasture infectivity with trichostrongylid larvae in the northern Guinea Savanna of Nigeria.

For the study of pasture infectivity in the northern Guinea Savanna of Nigeria, variable numbers of helminth-free tracer lambs grazing an unimproved pasture were slaughtered monthly throughout a period of 12 months. The numbers of worms recovered showed that large numbers of infective trichostrongyle larvae were ingested with the pasture from June till October. Infectivity started to decline from November until the end of January after which the pasture became completely free of parasitic nematode larvae and remained so until the end of May.

Termination of arrested development of the trichostrongyles of sheep in northern Nigeria.

Monthly worm counts of groups of ewes and lambs that grazed continuously and tracer lambs revealed that under the conditions existing in northern Nigeria, most of the Haemonchus contortus in sheep between November and March were arrested larvae. During the months of April and May, almost equal proportions of adults, developmental stages and arrested larvae were recovered and, by June, only adults and developmental stages were recovered in high numbers. The proportion of arrested larvae had diminished considerably. A similar pattern was recorded for Trichostrongylus spp, except that fewer larvae were involved in arrested development and very large numbers of adults were recovered throughout the duration of the study. Maturation of arrested larvae occurs in April.

Inhibited development of trichostrongylids of sheep in northern Nigeria.

Worm counts from Yankassa ewes, lambs and tracer lambs grazing unimproved pasture at Zaria were obtained each month during the rainy season of 1976. In June and July up to 14 per cent of the Haemonchus contortus populations consisted of early fourth stage larvae (L4). In August this increased to more than 55 per cent and in October to more than 95 per cent. From June to August most of the abundant late L4 contained rodlike crystals. More than 95 per cent of the Haemonchus contortus populations of two lambs killed two weeks after infection with infective larvae, cultured for seven days at 25 degrees to 30 degrees C in the dark, were early L4. Inhibited 3rd stage Trichostrongylus spp did not exceed 26 per cent of the worm populations.

Changes in blood values of sheep suffering from acute and chronic helminthiasis.

Systematic blood changes in two groups of sheep, one suffering from acute and the other from chronic helminthiasis were studied. In the group with acute infection, there was a rapid increase in helminth egg output coupled with rapid decline in the values of packed cell volume (PCV), haemoglobin (Hb) and red blood cells (RBC). Fluctuations were observed in the value of white blood cells (WBC). In the group with chronic infection, a slow and unsteady increase in helminth egg output was accompanied by a slow and steady fall in the values of PCV, Hb and RBC. As with acute infection, the value of WBC was unsteady.

Efficacy of thiophanate and thiabendazole against inhibited trichostrongylid larvae in sheep.

In a trial with natural infections of trichostrongyles in sheep, thiophanate and thiabendazole at 100 mg/kg and 200 mg/kg bodyweight were highly effective in removing all stages of development of the helminths including the inhibited stages. At 50 mg/kg bodyweight however, both drugs were only capable of reducing helminth load.