Characterization of trypanosome isolates from naturally infected horses on a farm in Kenya.

Following an outbreak of trypanosomosis in horses on a farm in Kenya, 18 trypanosome isolates were collected from the infected animals over a period of one and a half years and cryopreserved for characterization. The characterization was done on the basis of morphology using Giemsa-stained blood and buffy coat smears, infectivity to mice, recombinant DNA hybridization, and chromosome separation by orthogonal field alternation gel electrophoresis (OFAGE). Morphologically, all the trypanosome isolates were identified as belonging to the subgenus Nannomonas, and a total of 16 out of the 18 isolates grew in mice. Using the recombinant DNA hybridization technique, the isolates were further classified as the 'savannah' type of Trypanosoma congolense. Furthermore, chromosome separation by OFAGE, carried out on six clones derived from different isolates, exhibited a profile characteristic of T. congolense, 'savannah' type. However, there were differences in the number and positions of the medium-sized and minichromosomes indicating a diversity of serodemes within the isolates. Hence the infecting trypanosomes in this disease outbreak were T. congolense, 'savannah' type, and comprised several serodemes or strains.

Use of antigen capture tube enzyme-linked immunosorbent assay for the diagnosis of Trypanosoma evansi infections in dromedary camels (Camelus dromedarius).

Parasitological diagnosis of Trypanosoma evansi infection in camels is hampered by the small number of parasites in blood circulation, coupled with the tendency of this trypanosome to invade tissues. To overcome this, a more sensitive assay, an antigen enzyme-linked immunosorbent assay (ELISA), was developed, capable of detecting trypanosome antigens released into the bloodstream by dying parasites. To evaluate the usefulness of this assay in assisting chemotherapy, an experiment was designed to compare the ability of a Trypanozoon subgenus-specific monoclonal antibody (TR7) to capture antigens in whole blood and serum of camels in a T. evansi-endemic area of the Marsabit district in northern Kenya. The tests were performed in polystyrene tubes coated with TR7. Antigen ELISA using whole blood was performed in the field, while serum collected on the same day from the same animals was stored at -20 degrees C and tested in the laboratory at a later date. A total of 100 camels were examined. Twelve per cent of the camels were found to be antigenaemic when whole blood was tested, compared to thirteen per cent detected using serum. Thus, the results obtained so far do not show a significant difference in the sensitivity of tube ELISA when detecting antigens either in whole blood or serum.

Assessment of bovine hoof conformation and its association with lameness, animal factors and management practices on small-scale dairy farms in Kiambu district, Kenya.

Digital health and conformation were assessed in 216 dairy cattle on 78 randomly selected small-scale farms. For each cow, gait was assessed and the digits examined in detail. Hoof measurements (angle and length of the dorsal hoof wall, heel depth and hoof-base area) were also made. Hoof measurements varied most between individual cattle. Dorsal angle was correlated with heel depth (r = 0.53; P = 0.001) and dorsal length (r = -0.40; P = 0.001). The hoof-base area was correlated with the dorsal length (r = 0.41; P = 0.001). There were significant breed differences in dorsal angle (P = 0.03) and dorsal length (P < 0.01). The dorsal angle was correlated with parity and body condition, while the dorsal length, heel depth and the hoof-base area were correlated with the heart girth (P < 0.01). Hoof conformation was associated with both clinical lameness and hoof lesions. A 1-cm increase in the dorsal length increased the odds of lameness by 16.9, heel erosion by 1.8, underrunning by 5.4 and overgrowth by 40 (P < 0.01).

Necrosis and sloughing of skin associated with limb cellulitis in four cows and a calf: predisposing causes, treatment and prognosis.

Four cows and a calf with non-suppurative limb cellulitis were observed subsequently to suffer skin necrosis and sloughing in the affected limbs, either on or distal to the metacarpus or metatarsus. In comparison with six cows with suppurative Corynebacterium pyogenes limb cellulitis, topical therapy or the cases with skin necrosis and sloughing was adequate and the prognosis was good, when compared with the rigorous systemic therapy applied to the cows with suppurative cellulitis, some of which died. The skin necrosis and sloughing resulting from limb cellulitis seemed to be encouraged by the paucity of tissue between the skin and the bone, by the poor vascularity of the area, and by the causative bacteria.

Healing of dehorning wounds.

Open wound healing following dehorning using a wire saw was observed in 25 cattle aged between 1 and 5 years. Initially, there was a marked thickening of the scab over the wound as a ridge near the skin margin. A pale yellow to pink membrane then developed from the sides of the frontal sinus opening. Granulation tissue formed to fill the frontal sinus opening before healing by epithelization, followed by wound contraction. In some animals a bony horn stump projecting about 2-3 mm above the wound surface appeared which underwent osteosis; the dead bone gradually loosened and fell off during the healing process; histological sections revealed the presence of numerous osteoclasts lining the bone spicules. The presence of the frontal sinus and the stump of the horn processes left after dehorning are factors that make the healing of an open dehorning wound unique compared with other wounds.

Trypanosoma brucei, T. congolense and T. vivax infections in horses on a farm in Kenya.

Equines are particularly susceptible to infection with Trypanosoma evansi and T. brucei, but rarely is natural T. congolense and T. vivax infection seen in horses. An outbreak of trypanosomosis occurred in a herd of horses used for patrolling the pineapple fields on the Del Monte Farm, Thika, Kenya initially involving 6 horses. On subsequent screening of the entire group, T. brucei, T. congolense and T. vivax infections were detected in 16 of the 35 horses. The tests used for diagnosis included microscopic examination of stained blood smears, buffy coat technique, mouse inoculation and antigen detection enzyme immunoassay (antigen ELISA).

Response of diminazene-resistant and diminazene-susceptible Trypanosoma congolense to treatment with diminazene when occurring as a mixed infection in goats.

A study was carried out to determine whether a drug-resistant trypanosome population could influence the survival of a drug-sensitive population in mixed infections in goats. To identify both populations during the course of a mixed infection, a system for distinguishing them was developed; using a nucleotide sequence of a cDNA that was derived from Trypanosoma congolense ILNat 3.3 (IL 1616), a pair of 20-mer primers was designed which, in a PCR, amplified a 900-bp sequence from the diminazene-sensitive trypanosome, T. congolense IL 1180, but not the diminazene-resistant trypanosome, T. congolense IL 3247. The PCR technique detected 100 pg of IL 1180 DNA when mixed with 25 ng of total genomic DNA of IL 3274, as determined by gel electrophoresis and ethidium bromide-staining of the PCR products. Using the 900-bp PCR product as a 32P-labelled probe on Southern blots, the sensitivity was increased 100-fold. Three groups of five goats each were infected with IL 1180 (group A), IL 3274 (group B) or both clones simultaneously (group C), and treated with diminazene aceturate at a dose of 7.0 mg/kg body weight following detection of trypanosomes. Three other groups of three goats each were similarly infected and kept as untreated controls. All group A animals were cured, while all in group B and four animals in group C relapsed. Trypanosomes were harvested from all animals at regular intervals up to 60 days post treatment. Using the PCR techniques, IL 1180 DNA could not be detected in any post-treatment trypanosome DNA sample. It therefore appeared, on the basis of the sensitivity of the DNA detection systems used, that IL 1180 is unable to survive treatment with diminazene aceturate when mixed with IL 3274 in goats.