Identification and characterization of sialidase-like activity in the developmental stages of Amblyomma variegatum.

Amblyomma variegatum F. are obligate hematophagous ectoparasites of livestock that serve as the vectors of Ehrlichia ruminantium (formerly known as Cowdria ruminantium), the causative agent of heartwater disease. In the light of the fact that they are blood-feeding, their salivary glands play prominent role in their acquisition of nutrients from the bloodmeal. Sialic acids are a major component of glycoprotein in mammalian blood fluid and cells. Sialome of hard ticks is still sparse. Here, for the first time, the possible expression of sialidase in A. variegatum was investigated. Our finding established the presence of type II sialidase-like activity in the three stages (larva, nymph, and adult) of the fed and unfed tick. There was no statistically significant difference in sialidase activity in the various stages of this ectoparasite (P > 0.05). The enzyme was purified by combination of salting out and ion exchange chromatography on DEAE--cellulose and hydroxylapatite columns. Characterization of the enzyme revealed that it is optimally active at 40 degrees C and pH 5.5, and is activated by bivalent cations Zn2+ or Fe2+. The enzyme has a Km of 0.023 mM and Vmax of 0.16 millimol/min with Fetuin as the substrate. To assess the susceptibility of some mammalian cells to the tick sialidase, we prepared erythrocyte ghost cells from different animals, which were incubated with the enzyme. Results revealed that the ruminant cells were better substrates. Our work and findings contribute to the preliminary characterization of the A. variegatum salivary proteome, and may pave way to the development of new acaricides.

Study on the susceptibility of Sahel goats to experimental Trypanosoma vivax infection.

Sahel goats, also known as Borno whites are found in the northern semi-arid, tsetse free Sahel region of Nigeria. They are transported alongside cattle from this zone to all other zones in the country, including the tsetse-infested zones, for commercial purposes and are kept for some time in these tsetse-infested zones until they are sold. This study therefore assessed the susceptibility of this breed of goats to trypanosome infection and its response to treatment with Berenil. Six bucks were inoculated intravenously with Trypanosoma vivax through the jugular vein while two served as uninfected control. The mean pre-patent period was 4.5 days and increasing parasitaemia followed the establishment of infection. Onset of parasitaemia was associated with increase in rectal temperature in all the infected goats and the temperature peak coincided with the only parasitaemic peak second week post-infection. The infected goats were treated with Berenil (Hoechst, Germany) 3.5mg/kg body weight at 4 weeks post-infection. The packed cell volume (PCV) continued to fall from a mean 30.73+/-0.01% pre-infection to a mean 13.21+/-0.18% at 1 week post-treatment. Deaths were recorded for 4 of the infected goats 1 week post-treatment while the remaining two died 2 weeks post-treatment, not responding to treatment.

Erythrocyte osmotic fragility and lipid peroxidation following chronic co-exposure of rats to chlorpyrifos and deltamethrin, and the beneficial effect of alpha-lipoic acid.

The present study aimed to evaluate the effect of chronic co-exposure to chlorpyrifos (CPF) and deltamethrin (DLT) on erythrocyte osmotic fragility, lipid peroxidation and the ameliorative effect of alpha-lipoic acid (ALA) on erythrocyte fragility. Thirty-six male Wistar rats divided into six groups of six rats each were used for the study. Groups I (S/oil) and II (ALA) were given soya oil (2 ml/kg) and ALA (60 mg/kg), respectively. Rats in group III (DLT) and IV (CPF) were exposed to DLT (6.25 mg/kg) and CPF (4.75 mg/kg) (1/20th of the previously determined LD50 of 125 mg/kg and 95 mg/kg, respectively, over a period of 48 h). Rats in group V (CPF + DLT) were co-exposed to CPF (4.75 mg/kg) and DLT (6.25 mg/kg), while those in group VI (ALA + CPF + DLT) were pretreated with ALA (60 mg/kg) and then co-exposed to CPF and DLT, 45 min later. The treatments were administered by gavage once daily for a period of 16 weeks. Blood collected at the end of the experimental period were analyzed for erythrocyte osmotic fragility and malondialdehyde (MDA) concentration. The study showed that chronic co-exposure to CPF and DLT resulted in an increase in erythrocyte fragility and MDA concentration which were ameliorated by supplementation with alpha-lipoic acid. The study concluded that repeated co-exposure to CPF and DLT elevated erythrocyte fragility probably due to increased lipid peroxidation, and pretreatment with alpha-lipoic acid ameliorated these alterations.

Hemotoxicity induced by chronic chlorpyrifos exposure in wistar rats: mitigating effect of vitamin C.

The study evaluated the ameliorative effect of vitamin C on chronic chlorpyrifos-induced hematological alterations in Wistar rats. Twenty adult male rats divided into 4 groups of 5 animals each were exposed to the following regimens: group I (S/oil) was administered soya oil (2 mL/kg b.w.), while group II (VC) was given vitamin C (100 mg/kg b.w.); group III was dosed with CPF (10.6 mg/kg b.w.); group IV was pretreated with vitamin C (100 mg/kg) and then exposed to CPF (10.6 mg/kg b.w.), 30 minutes later. The regimens were administered by oral gavage once daily for a period of 17 weeks. Blood samples collected at the end of the study revealed reduction in the levels of pack cell volume, hemoglobin, red blood cells, leukocytes (attributed to neutropenia, lymphopenia, and monocytopenia), and platelets in the CPF group, which were ameliorated in the vitamin C- pretreated group. The elevated values of malonaldehyde, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and neutrophil/lymphocyte ratio in the CPF group were restored in those pretreated with vitamin C. The study has shown that chronic CPF-induced adversity on hematological parameters of Wistar rats was mitigated by pretreatment with vitamin C.

Ameliorative effect of vitamin C on chronic chlorpyrifos-induced erythrocyte osmotic fragility in Wistar rats.

Chronic exposure to chlorpyrifos (CPF) has been shown to cause increased lipoperoxidative changes in the erythrocyte membranes. The relationship between chronic CPF-induced lipoperoxidative changes and erythrocyte fragility has not been elucidated. The aim of the present study is to evaluate the role of lipoperoxidation on CPF-induced erythrocyte fragility and the ameliorative effect of vitamin C. Twenty animals divided at random into four groups of five animals each served as subject for this study. Rats in group I served as the control group and were given only soya oil at a dose of 2 mL/kg body weight (b.w.). Rats in group II were dosed with vitamin C (100 mg/kg b.w.) and then supplemented with soya oil (2 mL/kg b.w.), while those in group III were administered with CPF only at a dose of 10.6 mg/kg b.w. (~one-eighth of the previously determined median lethal dose [LD(50)]). Rats in group IV were pretreated with 100 mg/kg b.w. of vitamin C, and then dosed with CPF at a dose of 10.6 mg/kg b.w., 30 min later. The different treatment regimens were orally administered daily for a period of 17 weeks. Blood collected from the animals at the end of the test period were analyzed for erythrocyte osmotic fragility and malonaldehyde (MDA) concentration as an index of lipid peroxidation. The study showed that CPF caused significant increase in erythrocyte fragility and MDA concentration, which were ameliorated by pretreatment with vitamin C. In conclusion, the study showed that CPF-evoked erythrocyte fragility due to increased lipoperoxidative changes was ameliorated by pretreatment with vitamin C.