Evaluation of three different antigens in an indirect enzyme-linked immunoassay for the detection of antibodies against Brucella abortus SRB51 in vaccinated heifers

The live attenuated Brucella abortus SRB51 (SRB51) is a partial O-chain-deprived mutant. The relative lack of the polysaccharide prevents it from inducing antibodies detectable by most of the serological tests used for the diagnosis of bovine brucellosis. The performance of three antigens used in an indirect enzyme-linked immunoassay test for detecting SRB51 antibodies were evaluated. A homogeneous group of twenty-five 10-month-old Hereford heifers was used. The animals were bled on day 0 and then subcutaneously vaccinated with 2 ml of a commercially available SRB51 vaccine (Schering-Plough) containing 1x10(7) to 3.4x10(7) viable cells. Blood samples without anticoagulant for sera obtaining were then collected at days 30, 90, 210 and 360 post-vaccination. To detect the SRB51 antibodies, Brucella ovis hot saline extract, B. ovis RLPS (RLPS), and SRB51-RLPS were used. The buffered antigen plate agglutination test and an indirect enzyme-linked immunoassay (I-ELISA) using the smooth LPS (SLPS) antigen from B. abortus were used as control tests. All the sera samples were negative in the BPA test and in the standard I-ELISA using the SLPS. The SRB51-RLPS and the B. ovis RLPS antigens performed better than the B. ovis hot saline extract antigen.

Gizzard impaction in lesser rhea chicks (Pterocnemia pennata) raised on farms in Patagonia, Argentina

Impaction of the gizzard was diagnosed in 33 1-to-4-wk-old lesser rhea (Pterocnemia pennata) raised on farms in Patagonia, Argentina. The birds showed anorexia, lethargy, constipation, dehydration, weight loss, and weakness. Necropsy revealed gizzard impaction by fibrous material, sand, rocks, and rubbish. Also, excess fibrous material was observed in the small intestine, and intussusception was found in one chick. Impaction of the gizzard observed in the present study was similar to that reported in other ratite species and confirmed that this disease can affect lesser rhea chicks raised in captivity. This disease affected 33 out of 41 (80%) dead lesser rhea chicks submitted to the Animal Health Unit of The National Institute of Agricultural Technology, Bariloche, Argentina, during the study period, so it can be a significant cause of mortality in farmed rheas in Argentina.

Epidemiological observations in a Corriedale flock affected by Brucella ovis

Brucellosis in sheep, caused by Brucella ovis, is primarily a chronic infectious disease of rams with epididymitis as its most characteristic lesion. Six hundred rams from an infected farm were clinically and serologically examined once a year, over a 3-year period. An increase from 2.1% to 6.3% in the prevalence of animals serologically positive to B. ovis occurred over the 3 years. However, the prevalence of rams with lesions in the reproductive tract declined from 14.2% to 6.5% in the third year following one year of strict culling of clinically affected and rams that were serologically positive for B. ovis. Clinical lesions found in the 179 affected rams fell into two main categories: rams with epididymitis and rams with affected lymph nodes. These results suggest that the prevalence of the disease relates mainly to the sexual activity of the animal and not to age in itself. A single cull based on the results of clinical examination and serological test results was unable to decrease the prevalence of B. ovis in an extensive Corriedale sheep flock.

An attempt to reproduce 'mal seco' in horses by feeding them Festuca argentina

'Mal seco' is an almost invariably fatal disease of horses in Argentina and Chile, which resembles grass sickness, a dysautonomia of horses in Europe. The aetiology of mal seco remains unknown. An attempt to reproduce the disease was made by feeding horses with Festuca argentina, a plant considered to be toxic to animals and which was consistently found in the diet of nine horses suffering from mal seco. Three horses were fed with F argentina ad libitum for 28 days. The plant was infected with an endophytic fungus, whose morphological characteristics were in agreement with descriptions of Acremonium chlamydosporioides. No clinical abnormalities were observed in two of the horses, but one died on the fifth day of the trial after becoming incoordinated, unsteady and ataxic in the fore- and hindlimbs. No gross changes were observed post mortem in any of the horses, with the exception of a small number of Fasciola hepatica in the liver of the horse which died, and a moderate number of Gasterophilus species in the stomach of all three horses. No histopathological changes were observed in any of the organs examined, including several autonomic ganglia, brain including most brain stem nuclei, spinal cord, liver, kidney, stomach and small and large intestine. The results of this study suggest that F argentina is either not implicated in the aetiology of mal seco or produces its effects only when they are triggered by other unknown factors.

Evaluation of an indirect ELISA for the diagnosis of bovine brucellosis

Control and eradication of bovine brucellosis is usually based on the serological detection of antibodies. In Argentina, the rose bengal test (RB) and the buffered plate antigen test (BPA) are the 2 screening tests officially recognized, whereas the 2-mercaptoethanol test (2ME) and the tube agglutination test (SAT) are the confirmatory assays currently in use. In order to improve the serological diagnosis of bovine brucellosis in Patagonia, Argentina, an indirect enzyme-linked immunosorbent assay (I-ELISA) kit distributed by the International Atomic Energy Agency was evaluated. Sera from negative nonvaccinated, negative but vaccinated, and positive animals were tested by all the above techniques. The specificity of the I-ELISA (98.9% and 97.2%) was similar to that of the BPA, RB, 2ME and complement fixation (CF) tests when used to test sera from negative nonvaccinated and negative but vaccinated animals, respectively. The sensitivity of the I-ELISA (98.7%) was higher than the BPA test (96.1%) and the CF test (95.2%). The I-ELISA kit evaluated in this study was thought to be a valuable tool for the diagnosis of bovine brucellosis in the Patagonia region where little epidemiological information is available about this disease, and where large numbers of sera should be tested to obtain such information.

Histopathology of the brain-stem nuclei of horses with "Mal seco", an equine dysautonomia

"Mal seco" is a disease of unknown aetiology affecting horses in Argentina. It is similar to grass sickness, a primary dysautonomia of horses in Europe. A histopathological study of the brain stem nuclei of three horses with "mal seco" was performed. Changes were found that consisted of chromatolysis, cytoplasmic vacuoles, eosinophilic sphaeroids, and pyknotic and eccentric nuclei. These changes were most severe at the oculomotor, vestibular and abducent nuclei. The results provide further evidence to suggest that "mal seco" and grass sickness may be the same disease.

An outbreak of enterotoxaemia caused by Clostridium perfringens type D in goats in Patagonia

Forty-four of a flock of 117 angora goats in the Rio Negro province of Argentina died within four days. Most of the animals died shortly after the onset of clinical signs, but in a few the clinical course lasted for several days. Post mortem the small and large intestines were filled with watery contents, blood and fibrin clots, and there were numerous ulcers on the mucosa. Small areas of malacia were observed histologically in the brain. Clostridium perfringens type D in pure culture was isolated from the kidneys and gut contents of the affected animals. Epsilon toxin was identified by the mouse seroneutralisation test in the supernatant solution from cultures of these isolates and in the intestinal contents of the affected animals. Heavy infestations with coccidia, nutritional and environmental stress, and an anthelmintic overdose were possible predisposing factors for the outbreak.

Mal seco, a grass sickness-like syndrome of horses in Argentina

Mal seco is a grass sickness-like syndrome of horses which has mainly been observed in Patagonia, Argentina, although some reports indicate that the disease may exist in other Argentinian provinces and in the south of Chile. The aetiology of mal seco remains unknown but the disease seems to be restricted to animals grazing on natural pastures and not receiving supplementary feeding. Mal seco is clinically characterized by total or partial bowel stasis and the main findings at post-mortem examination are almost exclusively restricted to the bowel. The most striking histopathological changes found consisted of degenerative changes in the coeliaco-mesenteric ganglia and also in other central and peripheral structures of the nervous system.

Bacillary haemoglobinuria diagnosis by the peroxidase-antiperoxidase (PAP) technique

A peroxidase-antiperoxidase (PAP) technique was used to diagnose bacillary haemoglobinuria in formalin-fixed, paraffin-embedded liver tissues of cattle. The PAP method revealed Clostridium haemolyticum in the zone of liver necrosis characteristic of the disease and also in culture smears of this microorganism, but C. novyi type B, C. chauvoei, C. septicum and C. perfringens types B and C remained unstained by the PAP reaction. The PAP technique performed provides a specific, simple and rapid method to diagnose bacillary haemoglobinuria.

Histopathological changes in the coeliaco-mesenteric ganglia of horses with 'mal seco', a grass sickness-like syndrome, in Argentina

'Mal seco' is a grass sickness-like syndrome of horses in Argentina. A histopathological study was made of the coeliaco-mesenteric ganglia of four horses with 'mal seco' and of four horses that died from other causes. The severity and extent of the lesions found in the horses with 'mal seco' was greatest in the two with the shortest clinical course. Degenerative changes consisted mainly in the loss of Nissl substance, cytoplasmic vacuoles, neuronophagia, intercellular and intracytoplasmic eosinophilic bodies, and pyknotic and eccentric nuclei. The coeliaco-mesenteric ganglia of the control horses had no histological lesions. The histological lesions in the horses with 'mal seco' were very similar to those described in the coeliaco-mesenteric ganglia of horses with grass sickness in Europe and it is suggested that 'mal seco' and grass sickness may be the same disease.