Testing albendazole resistance in Fasciola hepatica: validation of an egg hatch test with isolates from South America and the United Kingdom.

The main goal of the current work was to develop and validate an in vitro fluke egg hatch test, as a method for the detection of albendazole (ABZ) resistance in the liver fluke, Fasciola hepatica. Fluke eggs (200/ml, n= 5) from six different isolates were used in the current experimental work. They were obtained from different geographical locations and named Cullompton (UK), CEDIVE (Chascomus, Argentina), INTA-Bariloche (Bariloche, Argentina), Rubino (Uruguay), Cajamarca (Perú) and Río Chico (Catamarca, Argentina). The fluke eggs were incubated (25 °C) for a 12-h period in the presence of either ABZ or its sulphoxide metabolite (ABZ.SO) (5, 0.5 or 0.05 nmol/ml). Untreated eggs were incubated as a control. Incubated eggs (with or without drug present) were kept in darkness at 25 °C for 15 days. Afterwards, the trematode eggs were exposed to daylight over a 2-h period. Hatched and unhatched eggs were evaluated using an optical microscope, and the ovicidal activity was assessed for each fluke isolate. A very low ovicidal activity ( ≤ 13.4%) was observed in the ABZ-resistant CEDIVE isolate for both ABZ and ABZ.SO. Conversely, in the INTA-Bariloche and Río Chico isolates, which are suspected to be susceptible to ABZ, ovicidal activities ≥ 70.3% were observed after incubation with ABZ at the lowest concentration tested (0.05 nmol/ml). This finding correlates with that previously described for the ABZ-susceptible Cullompton. Finally, the Cajamarca and Rubino isolates behaved as ABZ resistant, since no ovicidal activity was observed after eggs were incubated with ABZ at 0.5 nmol/ml. Considering the specific results obtained for each isolate under assessment, the egg hatch test described here may be a suitable method for detection of ABZ resistance in F. hepatica.

Resistance of Fasciola hepatica against triclabendazole in cattle in Patagonia (Argentina).

In the winter of 2008, cattle on a farm in the province of Neuquen, Argentina died from subacute and chronic liver fluke disease despite four previous treatments with Triclabendazole (TCBZ). In the spring of 2009, a preliminary efficacy test revealed good performance using nitroxynil, whereas TCBZ efficacy was only 18% by egg counts of Fasciola eggs in the faeces. Resistance to Fasciola hepatica to TCBZ has never been reported in South America, so in January of 2010 a controlled trial was conducted to confirm and to define the degree of resistance in this herd. In a clinical trial, the fluke egg output was monitored on Days 14 and 21 and serum enzymes gamma-glutamyl transpeptidase (GGT) and glutamic-oxaloacetic transaminase (GOT) on Days 0 and 21 in 36 calves treated with TCBZ or with closantel. The results showed a reduction of 100% in fluke egg output at Days 14 and 21 for closantel. The mean epg in the TCBZ-treated groups did not decrease. Because of the fact that in this study TCBZ treatment in cattle had no effect, even at double the recommended dose, it is highly indicative that resistance of F. hepatica against TCBZ is present on this farm. The GGT and GOT levels decreased in the closantel-treated group as a result of the treatment at 21 days after dosing. To evaluate the importance of TCBZ resistance in F. hepatica in Argentina, a study on more farms from endemic areas is needed.

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 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.

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.

Interference with sawfly (Arge pullata) poisoning in Fasciola hepatica-infected lambs.

Lambs harbouring an 8-week-old infection with Fasciola hepatica, together with fluke-free animals, were dosed orally with 2 g per kg body weight of sawfly larvae (Arge pullata). Fluke-free, non-dosed lambs and lambs infected only with F. hepatica served as controls. Clinico-pathological observations on sawfly-dosed, fluke-free lambs revealed the characteristic picture of sawfly poisoning. Four of six animals had to be killed in extremis. In contrast, sawfly-dosed, fluke-infected lambs exhibited only moderate clinico-pathological signs of sawfly poisoning and no deaths occurred. A reduction in the sawfly-induced liver pathology as a consequence of the concurrent F. hepatica infection was also noted. Possible factors responsible for the antagonistic effect of F. hepatica infection on sawfly poisoning in lambs are discussed.

A comparison of the filtration, concentration, and thick smear techniques in the diagnosis of Schistosoma bovis infection in cattle and goats.

The syringe and the modified Bell filtration techniques, the cellophane faecal thick smear (Kato/Katz) and Teesdale (sandwich) smear techniques, and the formol-ether concentration technique were compared for efficiency for detection of eggs of Schistosoma bovis in faeces from cattle and goats. Both filtration techniques were highly effective as revealed by high sensitivity and mean egg counts. However, efficiency declined markedly using formalin-fixed faecal material. The efficiency of the Teesdale technique was comparable to that of the filtration techniques, whereas the efficiency of the Kato/Katz technique in goats and the formol-ether concentration technique in cattle was markedly lower. The ease of performance combined with the high sensitivity make the syringe filtration and the Teesdale techniques recommendable for field diagnosis of schistosomiasis in domestic stock.

Efficacy of piperazine dihydrochloride against Ascaris suum and Oesophagostomum species in naturally infected pigs.

A controlled trial was performed to evaluate the efficacy of piperazine dihydrochloride in a new granular formulation (Ascarex D) against naturally occurring infections with Ascaris suum, Oesophagostomum dentatum and O quadrispinulatum. Treatment effects were estimated on the basis of parasites recoverable from the intestinal contents. Given orally at 200 mg per kg body weight the compound showed an efficacy of 99 to 100 per cent against A suum and the nodular worms. Egg excretion of the respective species was reduced by 98 per cent and 100 per cent six days after treatment. No adverse reactions were observed after the treatment.