The early detection of peste-des-petits-ruminants (PPR) virus antigens and nucleic acid from experimentally infected goats using RT-PCR and immunocapture ELISA techniques.

Goats were infected subcutaneously with different African and Indian isolates of peste-des-petits-ruminants virus. Typical signs of disease were recorded from day 6 post infection for all isolates. Ocular, nasal and mouth samples were tested for the presence of virus antigen or nucleic acid using the immunocapture ELISA (ICE) and the RT-PCR technique. Using ICE, virus antigen was detected at day 4 in ocular and nasal samples of goats infected with Côte-d'Ivoire 89 and in the ocular, nasal and mouth samples with the India, Calcutta strains. By day 5, all samples from both these groups were positive while ocular and nasal samples from groups with Sudan-Sennar and Nigeria 75/1 strains became positive. With the RT-PCR technique virus nucleic acid, presumed to be associated with infectious virus excretion, was detected at day 3 in oral and nasal samples in groups infected with Côte-d'Ivoire 89 and India-Calcutta strains. From day 6-9, all samples from all groups were positive with both techniques. This experiment demonstrated that PPR virus antigens and nucleic acid, presumed to be related to infectious virus, is excreted 2-3days before the appearance of clinical signs whatever the technique used which is of epidemiological importance in controlling the spread of the disease. The ICE being easier to perform in developing countries can be recommended as a useful method to investigate PPR in small ruminants flocks at an early stage to prevent the diffusion of the disease.

The first specific detection of a highly pathogenic avian influenza virus (H5N1) in Ivory Coast.

The Virology Laboratory of the Central Laboratory of Animal Diseases in Ivory Coast at Bingerville received samples of wild and domestic avian species between February and December 2006. An RT-PCR technique was used to test for avian influenza (AI) and highly pathogenic AI subtype viruses. Among 2125 samples, 16 were type A positive; of which, 12 were later confirmed to be H5N1. Fifteen of these 16 type A positive samples were inoculated into the chorioallantoic cavity of 11-day-old embryonated hens' eggs for virus isolation. Eight produced virus with hemagglutination titres from 1/64 to 1/512. The 4/16 M-RT-PCR positive samples, which were H5N1 negative, were shown to be H7 subtype negative. The diagnostic efficiency of the laboratory for the surveillance of H5N1 in Ivory Coast was demonstrated. The positive cases of H5N1 were from a sparrowhawk (Accipter nisus); live market poultry and in free-range poultry, where the mortality rate was approximately 20% (2/10) and 96.7% (29/30) respectively. Currently, investigations into intensive poultry farms have proved negative for H5N1. No human cases have been reported this time.

Observations on rinderpest and rinderpest-like diseases throughout West and Central African countries during rinderpest eradication projects.

Between 1998 and 2005, the Regional Reference Laboratory at Bingerville (Ivory-Coast) received samples for analysis from Western and Central African countries. From a total of 606 sera; 65 tissue samples and 75 swabs received, no rinderpest virus or specific gene products or antibodies against rinderpest were detected. Use of the PCR on the tissue and swabs (total of 140 samples) identified the genomic presence of BVD (4/140), MCF (2/140), IBR (1/140) and FMD (6/140) viruses. These cause diseases that produce similar clinical signs to rinderpest. The quality of many samples sent to the reference laboratory did not meet the laboratory requirements and this compromised analysis of some specimens.

Evaluation of the virulence of some strains of peste-des-petits-ruminants virus (PPRV) in experimentally infected West African dwarf goats.

Different isolates of peste-des-petits-ruminants virus (PPRV) from outbreaks in Africa and India were investigated for virulence in West African dwarf goats in the Ivory Coast. Six groups of five animals received a virulent suspension of various strains of virus at a concentration of 10(3) TCID(50)/mL and the goats were observed for 15 days after infection. The Côte-d'Ivoire 89 (CI89), Guinea Conakry and Bissau Guinea PPRV strains caused a peracute disease; the India-Calcutta strain caused acute disease; the Sudan-Sennar strain produced an acute to mild disease, while the Nigeria 75/1 wild-type strain caused a mild disease and the animals recovered. The viruses studied contained examples of PPRV from specific lineage groups based on their nucleoprotein PPRV gene. This experiment indicated that virulence characteristics might be a useful marker to help classify PPRV isolates.

Early detection of viral excretion from experimentally infected goats with peste-des-petits ruminants virus.

We observed 15 goats for 9 days after subcutaneous infection with 10(3) TCID(50) with isolates of peste-des-petits ruminants virus from Africa and India and five concurrent, uninfected control goats. Typical clinical signs of the infection were present in all 15 infected goats by day 8 and in most by day 6 and some signs were present by day 4. However, 6 out of 15 goats already have detectable virus shedding by day 3 and four more were shedding by day 4 and every goat had virus shedding for at least 1 day before the recognition of clinical signs. This experiment indicates that incubatory carriers therefore might play a role in the transmission of PPRV among small ruminants.

Interference in the vaccination of cattle against rinderpest virus by antibodies against peste des petits ruminants (PPR) virus.

The ability of the attenuated vaccine 75/1 of peste des petits ruminants to interfere with rinderpest vaccination in cattle was investigated experimentally. Young cattle (93) were selected and tested as being negative for antibodies against RP or PPR viruses. These were vaccinated with the peste des petits ruminants attenuated vaccine strain PPR75/1. All animals produced specific antibodies against the peste des petits ruminants vaccine after one or two doses. The cattle were then vaccinated with attenuated rinderpest vaccine. Two months later, 88 of these animals were sampled and 21/88 were positive for antibodies specific for rinderpest. The 67 negative animals received a second rinderpest vaccine dose after which 31seroconverted. The 36 animals which failed to seroconvert were re-vaccinated, of these 28 seroconverted. This study highlights the interference by peste des petits ruminants vaccination, presumably through production of antibodies that cross react with the live rinderpest virus in the vaccine used. This interference is also observed after vaccination against rinderpest followed by subsequent administration of peste des petits ruminants vaccine.

Surveillance of wildlife as a tool for monitoring rinderpest and peste des petits ruminants in West Africa.

The authors provide a report on the surveillance of rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) in the wildlife population in Côte d'Ivoire. For this purpose, 266 animals from nine different species, selected according to susceptibility and abundance, were captured and sampled from Comoé, Marahoué and Lamto Parks. Two hundred and forty seven sera and 214 nasal swabs were collected and analysed by competitive enzyme-linked immunosorbent assay (cELISA) and reverse-transcriptase polymerase chain reaction (RT-PCR) techniques, respectively. Serological data demonstrated that RPV was not circulating within the national Parks and estimated the PPR seroprevalence to be less than 1%. The analysis of the nasal swabs revealed no cases of RPV infection, but PPRV infection was detected in four species, including buffalo. To minimise the cost of the study without affecting the sensitivity of the test, samples were pooled into different groups and submitted to RT-PCR using nucleoprotein gene specific primers. The RT-PCR used in this study, which was derived from the method developed by Couacy-Hymann et al. in 2002, was followed by a hybridisation step using internal specific probes to confirm the identity of the deoxyribonucleic acid product. When used in conjunction with a cELISA this method accurately demonstrated the absence of rinderpest viral persistence in Côte-d'Ivoire.