Short communication - Comparative study on peste des petits ruminants seroconversion level in sheep in Sudan.

Peste des petits ruminants (PPR) is endemic to Sudan. It is considered as a priority disease in the list of transboundary animal diseases (TADs). The aim of this study was to assess the reliability of the detection of PPR antibodies by a competitive enzyme-linked immunosorbent assay (cELISA) in naturally infected or vaccinated sheep. Sera were collected from 3,186 sheep from flocks located in six states of Sudan and additionally 100 sheep were vaccinated with a PPR homologous vaccine (produced locally) in a quarantine station. The percentages of PPR antibody-positive sera from the field varied between 72% and 100%, according to state. All sheep vaccinated in the quarantine station were PPR-seropositive. This study shows, first, that the percentages of PPR-seropositive animals were all very high, whether naturally infected or vaccinated. It also shows the reliability of the cELISA test used in this study.

La peste des petits ruminants (PPR) est présente au Soudan à l'état endémique. Elle est considérée comme une maladie prioritaire parmi celles de la liste des maladies animales transfrontalières (TAD). Les auteurs présentent une étude visant à évaluer la fiabilité d'une épreuve immuno-enzymatique de compétition (cELISA) pour la détection d'anticorps dirigés contre le virus de la PPR chez des ovins infectés naturellement ou vaccinés. Des échantillons sériques ont été prélevés sur 3 186 ovins provenant de troupeaux de six provinces du Soudan ; en outre, 100 ovins ont été vaccinés contre le virus de la PPR dans une station de quarantaine en utilisant un vaccin homologue (produit localement). Le pourcentage de sérums de terrain dans lesquels des anticorps dirigés contre le virus de la PPR ont été détectés variait de 72 % à 100 % suivant les provinces. Tous les ovins vaccinés dans la station de quarantaine ont donné un résultat positif au test sérologique. Cette étude a révélé un pourcentage très élevé d'animaux possédant des anticorps contre la PPR, tant chez les animaux infectés naturellement que chez les animaux vaccinés. Elle a également démontré la fiabilité de l'épreuve cELISA utilisée dans l'étude.

La peste de los pequeños rumiantes (PPR), endémica en el Sudán, tiene consideración de enfermedad prioritaria en la lista de enfermedades animales transfronterizas. Los autores describen un estudio encaminado a evaluar la fiabilidad del ensayo enzimoinmunoanálisis de competición (ELISAc) como método de detección de anticuerpos contra el virus de la PPR en ovejas vacunadas o infectadas por vía natural. En primer lugar, se obtuvieron muestras de suero de 3.186 ejemplares de rebaños ovinos situados en seis estados sudaneses y se administró a otras 100 ovejas una vacuna anti-PPR homóloga (de producción local) en un centro de cuarentena. Después se determinó el porcentaje de sueros positivos (con anticuerpos) de entre las muestras obtenidas sobre el terreno, que oscilaba entre un 72% y un 100%, según el estado. Todas las ovejas vacunadas en el centro de cuarentena fueron seropositivas. El estudio mostró, en primer lugar, que los porcentajes de animales seropositivos eran siempre muy altos, ya se tratara de ovejas vacunadas o de animales infectados por vía natural. Asimismo, puso de manifiesto la fiabilidad de la técnica de ELISAc empleada en el estudio.

Parasitological and clinico-pathological profiles in friesian cattle naturally infected with Theileria annulata in Saudi Arabia.

Clinico-pathological profiles were studied in adult and young Friesian cattle naturally infected with Theileria annulata in the Qassim Region, Saudi Arabia. Sixty-two clinical cases of T. annulata infection in adult and young Friesian cattle were diagnosed during the period from August 1999 to July 2000. Symptoms observed were marked fever, swelling of superficial lymph nodes, inappetance, tachycardia, dyspnoea and weakness. The most prominent gross pathological features were jaundice, petechial and ecchymotic haemorrhages involving mucosal and serosal surfaces of many organs as well as body fat. A number of young and adult Friesian cattle undergoing lethal T. annulata infection developed lymphoma-like lesions in a manner similar to that of T. parva. The main histological findings were necrosis and severe lymphocytic infiltration. The spleen, lymph nodes and Peyer's patches were devoid of typical lymph nodules.

Biochemical profiles in Friesian cattle naturally infected with Theileria annulata in Saudi Arabia.

The biochemical parameters were studied in adult and young Friesian cattle naturally infected with Theileria annulatta in the Qassim Region, Saudi Arabia. Forty-three clinical cases of tropical theileriosis were studied, together with 40 clinically healthy Friesian cattle. Cattle clinically infected with T. annulata had significantly lower serum total protein, albumin, globulin, creatinine, calcium, phosphorus, magnesium, potassium, iron and copper concentrations and significantly higher AST activity and bilirubin concentration than the healthy cattle.

Haematological profiles in pure bred cattle naturally infected with Theileria annulata in Saudi Arabia.

The Abbott Cell Dyn 3500 haematology analyzer was employed to study haematological parameters in 41 adult and young Friesian cattle naturally infected with Theileria annulata in the Qassim region of Saudi Arabia. Comparison was made with clinically healthy adult and young Friesian cattle. Changes in blood parameters in T. annulata-infected cattle indicated severe macrocytic hypochromic anaemia, panleukopenia, lymphocytopenia, eosinopenia, neutropenia and thrombocytopenia but no reticulocytosis.

Drug resistance in Sudanese Trypanosoma evansi.

The drug sensitivities of 16 Trypanosoma evansi isolates from Sudan were examined using two different in vitro assays and rodent models. IC50 values (concentration which inhibited incorporation of 3H-hypoxanthine by 50%) obtained in a 40 h assay indicate that most of the isolates were resistant to suramin, a drug which has not been used in Sudan since 1975. Sensitivities for suramin in a 10-day-in vitro assay varied within a 124-fold range. The in vitro results were confirmed by infection/treatment experiments in mice. Sensitivities in vitro for quinapyramine varied within a 166-fold range. In mice, the least sensitive isolates were not cured with dosages up to 10 mg/kg quinapyramine. Based on in vitro results, all isolates appeared to be susceptible to isometamidium.

The effect of multiple transfers of immune serum on maturing Schistosoma bovis infections in calves.

To investigate the role of humoral factors in immunity, serum from cattle with naturally acquired immunity to Schistosoma bovis was injected intraperitoneally into calves that had been infected 4 weeks earlier with 10,000 S. bovis cercariae. Serum was injected weekly until 12 weeks post-infection to a total of 4,500 ml per calf and controls received normal serum or saline. No significant difference in worm or in faecal or tissue egg counts were seen in the three groups of recipients in spite of the observation that the serum donors had proved highly resistant to experimental challenge. In a second experiment, pre-infection or 4-, 8- or 12-week post-infection serum from donors given a single experimental infection with 10,000 S. bovis cercariae was injected intraperitoneally into groups of calves that had been infected 4 weeks earlier with 20,000 S. bovis cercariae. Injections were given weekly up to week 10 post-infection to a total of 2000-3500 ml serum per calf. In calves injected with immune serum there was a reduction in faecal and tissue egg counts and in the numbers of worms recovered as compared with the controls. In recipients of 8- and 12-week serum the reductions in faecal and tissue egg counts were higher than those in worm recovery, suggesting that 8- and 12-week post-infection sera contained factors capable of causing, in addition to worm death, suppression of worm fecundity. This provides further evidence of the importance of fecundity suppression in immunity to schistosomiasis.

Suppression of Schistosoma bovis egg production in cattle by vaccination with either glutathione S-transferase or keyhole limpet haemocyanin.

Two of the antigens which have shown vaccine potential in animal experiments against Schistosoma mansoni are glutathione-S-transferase (GST) and GP38, protective epitopes of which are shared with keyhole limpet haemocyanin (KLH). We therefore tested S. bovis GST and KLH for vaccine efficacy against S. bovis in the natural Zebu cattle host. In a preliminary experiment three vaccinations with a total of 1.39 mg of native GSTs of S. bovis induced specific antibody at the time of challenge as detected by Western blotting and ELISA and mean faecal egg counts between weeks 6-10 post-challenge were reduced by 56.4 to 82.5% compared to non-vaccinated controls. Mean adult worm recoveries and tissue egg densities in large intestine and liver samples were also reduced in the vaccinated group, but these differences were not statistically significant. In a subsequent experiment one group of calves was vaccinated with a similar schedule to that used above; a second group of calves was given only two injections of GST (total 0.48 mg protein); a third group of calves was vaccinated twice with a total of 2.0 mg KLH in PBS. All three vaccination schedules induced specific antibody. Both GST vaccination schedules induced significant reductions in faecal egg counts compared to non-vaccinated controls and in this experiment tissue egg densities were also significantly reduced. A striking finding, however, was that adult worm counts were not reduced by vaccination. An essentially similar outcome resulted from KLH vaccination, since there were significant reductions in faecal and tissue egg counts in the absence of a reduction in adult worm numbers.(ABSTRACT TRUNCATED AT 250 WORDS)

Serodiagnosis of infection with Trypanosoma evansi in camels in the Sudan.

Five diagnostic tests for infection with Trypanosoma evansi have been compared in groups of camels experimentally infected or exposed to natural infection in the Sudan. The correlation of positive results obtained by assays of IgM levels, the mercuric chloride test and the formol gel test with the presence of active infection was unsatisfactory, but there was a good correlation between results obtained using IFAT and ELISA and proven infection. Sera from a high proportion of apparently uninfected camels from endemic areas gave positive reactions with all 5 tests, possibly indicating inadequate parasitological diagnosis or persistence of antibody after unsatisfactory chemotherapy. It was concluded that serological tests using trypanosomal antigens to detect antibodies were more sensitive for diagnosis than indirect tests based on raised euglobulin levels. Serodiagnostic tests may therefore have a place in future programmes for surveillance and control of T. evansi infections in camels.