ASSESSMENT OF DONKEYS (Equus asinus) EXPERIMENTALLY INFECTED WITH Trypanosoma brucei (Federe isolate) AND TREATED WITH HOMIDIUM CHLORIDE AND ISOMETAMIDIUM CHLORIDE

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ASSESSMENT OF DONKEYS (Equus asinus) EXPERIMENTALLY INFECTED WITH Trypanosoma brucei (Federe isolate) AND TREATED WITH HOMIDIUM CHLORIDE AND ISOMETAMIDIUM CHLORIDE

 

Abstract: This study investigated the course of T. brucei (Federe isolate) experimental infection in donkeys and the therapeutic efficacy of two trypanocides against the infection. Twenty-eight apparently healthy donkeys (Equus asinus) of equal sexes, aged between 8 – 9 months, were purchased from a livestock market in Maigatari town, Jigawa State and used for the study. They were housed in a tick and fly-proof pen, and allowed to acclimatize for 4 weeks during which they were screened for presence of diseases, and were fed Imperata cylindrica grass, Andropogon gyanus hay, cereal bran and cotton seed cake with clean water and salt lick provided ad libitum. Thereafter, they were assigned at random to 4 groups; A (Infected Homidium chloride-treated, n=8), B (Infected Isometamidium chloride-treated, n=8), C (Infected untreated/positive control, n=6) and D (uninfected untreated/negative control, n=6). Groups A and B donkeys were further divided into subgroups A1 A2 and B1 B2, of 4 donkeys each, to represent treatments at acute (day 12) and chronic (day 24) phases of infection, respectively. Twenty-two donkeys (groups A, B and C) were infected through jugular venipuncture with 2 ml inoculum containing 2×106 T. brucei (Federe isolate) and evaluated for clinical signs, pathology and response to treatment. Parasitaemia was evaluated using the wet mount, haematocrit and mouse inoculation techniques, and blood was sampled every 3 days for parasitology and haematology while sera for biochemistry were harvested once weekly. Treatment with the trypanocides was at dose of 1 mg/kg 2.5% Homidium chloride (Novidium®) and 0.5 mg/kg 1% Isometamidium chloride (Sécuridium®) on days 12 and 24 post-infection. Donkeys were evaluated pre-infection, post-infection and post-treatment for changes in physiological parameters, body weight, haemato-biochemical parameters and pathology. Carcasses and internal organs were examined for gross lesions. Tissue sections of the organs were prepared and examined ix for changes in architecture. Organ impression, cerebrospinal fluid and brain squash smears were prepared and examined for tissue invasion by the parasite. Trypanosoma brucei produced clinical trypanosomosis in the donkeys with pre-patent and incubation periods of 2 – 3 and 2 – 6 days respectively. Two of the infected donkeys did not develop trypanosomosis. From day 4 post-infection, the infected donkeys manifested weakness, reduced feed intake, intermittent fever, tachycardia, increased respiratory rates, intermittent penile erection, dehydration, rough hair coat, lacrimation, weight loss, pale mucous membranes with recumbency. Respiratory rales on auscultation was predominant at the chronic stage. Parasitaemia recorded was 4.27 ± 0.45 parasites per field at day 3 post-infection and increased significantly (p<0.0001) to 26.20 ± 1.35ppf by day 12 pi. Weight loss was significant at the chronic stage. Post-infection, haematology revealed anaemia, with a significant (p<0.005) reduction in mean red cell count (5.87±0.40 to 3.35±0.30), haemoglobin concentration (11.88±0.61 to 8.50±0.61) and packed cell volume (38.13±3.36 to 24.38±1.88). There was significant (p<0.0001) increase in mean corpuscular volume (53.07±1.65 to 69.92±1.73) and a significant (p<0.002) decrease in mean corpuscular haemoglobin concentration (36.05±0.35 to 32.47±0.66) indicating a macrocytic hypochromic anaemia. Mean white blood cell count reduced significantly post-infection (11.62±0.90 to 7.55±0.71) while differentials revealed significant (p<0.05) reduction in neutrophils (44.79±1.31 to 31.23±1.06) and eosinophils (4.63±0.70 to 0.39±0.10), and a significant (p<0.05) increase in lymphocytes (47.29±1.50 to 67.20±1.09). Serum chemistry post-infection revealed minor changes in albumin, aspartate aminotransferase, alkaline phosphatase and blood urea nitrogen, suggesting the infection caused mild pathology. Alanine aminotransferase (ALT) levels increased post-infection and post-treatment. Creatinine levels significantly (p<0.01) increased (69.00±2.86 to 83.67±3.27) post-infection in group C donkeys. x There was significant (p<0.05) decrease in the total protein (67.28±2.93 to 60.43±0.69) and glucose levels (100.70±3.17 to 46.00±7.84) post-infection. Serum electrolyte alterations observed were hypocalcaemia post infection and hypercalcaemia post treatment, while sodium, chloride, potassium, phosphorus and bicarbonate levels showed non-significant (p>0.05) variations. Twenty-four hours following treatment of donkeys in groups A and B with Novidium® and Sécuridium® respectively, parasites were not detected. Relapse of infection with low parasitaemia levels was detected from day 27 post treatment in subgroups A1, A2, and B1. Repeated treatment using Novidium® at 1 mg/kg and double the initial 0.5 mg/kg dose of the Sécuridium® (1 mg/kg), eliminated the parasites. Gross lesions observed in the untreated donkeys were hydropericardium (600 ml), atrophy of fat, mucoid exudates in the bronchi, congested lungs and spleen, and splenic haemorrhages. Histopathological findings were mononuclear perivascular cuffing in the brain, congestion of the lungs, kidney congestion with glomerulonephritis and splenic congestion with haemosiderosis. Impression smears revealed no parasites on microscopy. Tissue sections of treated donkeys showed less pathology. This study confirms susceptibility of donkeys to T. brucei (Federe) infection. Treatment with the two trypanocides at recommended concentrations and doses was effective in eliminating the parasites, with blood parameters returning to pre-infection values. However, the drugs produced some biochemical alterations in the treated donkeys. Isometamidium chloride was observed to have a better therapeutic effect than Homidium chloride, and is suggested as first drug of choice in the treatment of T. brucei infection in donkeys.

 

ASSESSMENT OF DONKEYS (Equus asinus) EXPERIMENTALLY INFECTED WITH Trypanosoma brucei (Federe isolate) AND TREATED WITH HOMIDIUM CHLORIDE AND ISOMETAMIDIUM CHLORIDE

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