The control of coccidiosis in chickens, including immunoprophylaxis, chemotherapy, and nutritional aspect, are reviewed. Coccidiosis, a disease of universal importance, necessitates the discovery of new approaches or an improvement of available methods aimed at controlling its spread. The exploration of other suitable methods to prolong the life of present anticoccidial drugs, and avoid emergence of resistant strains of coccidia while pharmaceutical manufactures are working to develop new products is highlighted. Vaccination against coccidiosis may be one of the available control measures and the combination of the trickle in-feed approach with oocysts of attenuated strain will provide a powerful potential vaccine, but it still needs to determine the routes of delivering vaccine acceptable in the field condition.
The anti-malarial effect of an aqueous extract of Cymbopogon citratus, a Nigerian traditional medicinal plant, has been investigated in mice infected with plasmodium yoelii nigeriensis. The plant extract was found effective in suppressing malarial infection. Infected animals, orally given in drinking water 0.106 – 0.473 g ml-1 of the extract for 5 consecutive days after the disease had been established, were observed to be cleared of the malarial parasites 4 days after commencement of treatment. The mice, however, lived thereafter, for another 8-10 days before dying because only a low number of non-parasitized red-blood cells were left in the circulation. When on the other hand, the crude salt was injected i. p in doses of 1.0-1.5 g kg-1 for 3 consecutive days, it suppressed the infection during and 2 days after the extract treatment, at which time it was observed that the erythrocyte infection rate (EIR) started rising until the animals died at about 8 days post-treatment, that is, they survived 5-6 days longer than the non-treated (control animals). Chemoprophylactic action of the extract injected i. p prior to infection gave protection for about 72 hours. No adverse reactions were recorded when the drug plant was given orally, but certain reactions were noted when administered i. p to which they survived. The drug plant given i. p has an LD50 of 2.32 g kg-1 and the plant is schizontocidal in action. Chemical analysis of the extract revealed presence of alkaloids, saponins, tannins and simple sugars.
Loss of membrane integrity and intracellular esterase activity in Eimeria tenella sporozoites after exposure to polyether ionophorous antibiotics lasalocid (LAS), monensin-Na (MON) and nigericin (NIG) were analysed by means of flow cytometry (FCM) using one-dimensional frequency distribution of measured intracellular fluorescein fluorescence (520nm) and propidium fluorescence (640nm), respectively. The polyether antibiotics were dissolved in dimethylformamide (DMF) and adjusted to concentrations of 100, 10, 1 and 0.1 μg/ml by dilution with medium 199. Thereafter, freshly excysted sporozoites were exposed to the above mentioned drug concentrations for 20, 40 and 70min and analysed by FCM. Compared with the DMF (1%) control, sporozoites exposed to 100 μg/ml LAS for 20min showed a strong reduction of esterase activity and a high degree of membrane damage, as well as 10μg/ml LAS after 70min incubation. NIG had a similar activity profile with respect to membrane damage indicating that this polyether is a powerful ionophore in killing E. tenella sporozoites in vitro. In contrast, MON which is known to be a strong anticoccidial in vivo, exhibited only a weak effect on sporozoites in vitro, and there was a time and dose-dependent decrease of sporozoites showing enhanced esterase activity but no membrane damage.
An axenic culture system for Trypanosoma congolense bloodstream trypomastigotes was used for in vitro detection of their sensitivity to diminazene aceturate (DA), homidium chloride (HC), isometamidium chloride (IC) and quinapyramine sulphate (QS). Bloodstream trypomastigotes of 4 stocks (IL2079, IL2466, IL3266 and IL3338), 4 clones (IL1180, IL2642, IL3000 and IL3035) and 16 clones obtained in vitro from IL2079, IL2466, IL3000, IL3266, and IL3338, were propagated in vitro using HMI-93 medium (Hirumi and Hirumi 1991). Among these populations IL1180, IL2466, IL2642 are known to be sensitive to DA and/or IC as tested in mice and/or cattle, while IL3035 and IL3338 are highly resistant to DA, IC and/or HC when examined in cattle. Each well of a 24-well culture plate received 100 μl of distilled water containing various amounts of the drugs. Test plates were then freeze-dried and stored at room temperature. Levels of the resistance for each drug were then expressed in 10 steps from 10 to 1, denoting the following concentrations: DA at 600, 500, 400, 300, 200, 100, 80, 60, 40 and 20 ng/ml; HC, IC and QS at 10-fold serial dilutions from 10 μg to 10 fg/ml. Five hundred μl aliquots of trypanosome suspension in the medium, containing 4x105 trypanosomes/ml, were then placed in each well and maintained at 34℃ in a CO2 incubator for 5 days without medium change. Effects of the drugs were examined by phase-contrast microscopy every 24h. Growth inhibition of trypanosomes could be detected by day 3 and affected trypanosomes died during the next 24-48h. In contrast, trypanosomes which were resistant to the given concentrations continued to grow reaching the maximum population density by day 3-5, and died during the next 24h due to overgrowth. The pH indicator, phenol red, in medium in wells which contained affected populations indicated pH 8.0-8.5, while that in wells in which trypanosomes reached the maximum population density indicated pH6.5 by day 3-5. Colorimetry of the media on day 5 was thus also used to distinguish the drug sensitivity of trypanosome populations. Resistance levels of the 4 stocks and the 4 clones against DA, HC, IC and QS were IL1180: 4, 7, 6 ＆ 6, IL2079: 5, 6, 6 ＆ 6, IL2466: 4, 6, 6 & 8, IL2642: 2, 4, 3 & 5, IL3000: 5, 7, 7 ＆ 6, IL3035: 8, 7, 6 ＆ 8, IL3266: 4, 6, 5 ＆ 5 and IL3338: 8, 7, 7 ＆ 6, respectively. The levels of resistance of the in vitro cloned populations were similar to those of their parental populations. The information obtained in this system using 3 plates per drug per trypanosome population for 5 days provided an equivalent amount of information about the drug sensitivity of a trypanosome population as an in vivo test which uses 36 mice and lasts 2 months.