African Swine Fever Diagnosis Adapted to Tropical Conditions by the Use of Dried-blood Filter Papers.

The performance of Whatman 3-MM filter papers for the collection, drying, shipment and long-term storage of blood at ambient temperature, and for the detection of African swine fever virus and antibodies was assessed. Conventional and real-time PCR, viral isolation and antibody detection by ELISA were performed on paired samples (blood/tissue versus dried-blood 3-MM filter papers) collected from experimentally infected pigs and from farm pigs in Madagascar and Côte d'Ivoire. 3-MM filter papers were used directly in the conventional and real-time PCR without previous extraction of nucleic acids. Tests that performed better with 3-MM filter papers were in descending order: virus isolation, real-time UPL PCR and conventional PCR. The analytical sensitivity of real-time UPL PCR on filter papers was similar to conventional testing (virus isolation or conventional PCR) on organs or blood. In addition, blood-dried filter papers were tested in ELISA for antibody detection and the observed sensitivity was very close to conventional detection on serum samples and gave comparable results. Filter papers were stored up to 9 months at 20-25°C and for 2 months at 37°C without significant loss of sensitivity for virus genome detection. All tests on 3-MM filter papers had 100% specificity compared to the gold standards. Whatman 3-MM filter papers have the advantage of being cheap and of preserving virus viability for future virus isolation and characterization. In this study, Whatman 3-MM filter papers proved to be a suitable support for the collection, storage and use of blood in remote areas of tropical countries without the need for a cold chain and thus provide new possibilities for antibody testing and virus isolation.

Isolation of a non-haemadsorbing, non-cytopathic strain of African swine fever virus in Madagascar.

African swine fever (ASF) suspected clinically in Madagascar (1998-9) was confirmed by polymerase chain reaction (PCR) and nucleotide sequencing, following virus isolation. No haemadsorption or cytopathic effect could be detected following leukocyte inoculation, but viral growth in cells was confirmed by PCR. Detection of ASF virus genome was carried out by amplification of a highly conserved region coding for the p72 protein. Nucleotide sequencing of the amplicon revealed 99.2% nucleotide identity between the recent Malagasy strains and a virus recovered from the 1994 outbreak in Mozambique (SPEC265). A serological survey performed on 449 sera, revealed that only 5.3% of the sera taken from pigs between 1998 and 1999 were positive.

[African Swine Fever introduction into Madagascar, history and lessons from an emergence]. / Introduction de la Peste Porcine Africaine à Madagascar, histoire et leçons d'une émergence.

African Swine Fever (ASF) was diagnosed for the first time in Madagascar in 1998. ASF has apparently been introduced from the African continent to the southern part of the island with a subsequent spread to other regions except for areas in the north and in the west. The epidemic has had severe economic consequences for the home market of pork meat production. This article reviews the course of the epidemic with particular emphasis on the vectors involved in the transmission of the virus, such as the soft tick, Ornithodoros moubata porcinus. Presence of this vector and of the bushpig, Potamochoerus larvatus, as a potential wild reservoir, are some of the major obstacles in control of ASF in Madagascar. A veterinary disease surveillance system has to be urgently warranted.

Introduction de la peste porcine africaine à Madagascar : histoire et leçons d'une émergence

La Peste Porcine Africaine (PPA) a récemment fait son apparition à Madagascar.Officiellement diagnostiquée fin 1998, la PPA a vraisemblablement été introduite à Madagascar en 1997 dans le sud du pays à partir de virus provenant du continent africain. La PPA s'estensuite propagée dans la quasi-totalité du pays à l'exception de la région d'Antsiranana (Nord) et de Morondava (Ouest). La maladie a eu des conséquences économiques désastreuses et aentraîné la désorganisation de la filière porcine malgache.Nous rapportons ici l'histoire de cette émergence et l'existence de particularités locales comme la présence de vecteurs, les tiques du genre Ornithodoros - O. moubata porcinus - et de réservoirs sauvages potentiels comme le potamochère - Potamochoerus larvatus - qui compromettentl'éradication de la maladie.Ces faits renforcent la nécessité pour Madagascar de disposer d'un système d'alerte et de riposte rapide