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Five European reference laboratories participated in an exercise to evaluate the sensitivity and specificity of their routinely employed RT-PCR tests and cell cultures for the detection and isolation of foot-and-mouth disease (FMD) virus. Five identical sets of 20 coded samples were prepared from 10 vesicular epithelia, which were derived from submissions from suspect cases of FMD or swine vesicular disease (SVD). Sixteen samples were derived from six FMD virus positive epithelia representing four different serotypes (two each of types O and A and one each of types Asia 1 and SAT 2), two from samples which had been found to be negative by antigen ELISA and virus isolation (VI) in cell culture and two from SVD virus positive epithelia. Some of the FMD virus positive samples were prepared from 10-fold serial dilutions of three of the initial suspensions. Each laboratory tested the samples by one or more of its available RT-PCR procedures and inoculated cell cultures that it routinely uses for FMD diagnosis in attempts to isolate virus, the specificity of which was confirmed by antigen ELISA. The best of the RT-PCR assays used in each laboratory gave comparable results while the sensitivity of cell cultures was variable from high in one laboratory, moderate in two and low in two others. This prototype panel of samples would appear suitable for external quality assurance of these tests but would benefit from the inclusion of more negative samples and an extension in the serial dilution range of one or more of the FMD positive sample titration series.

Primary cells derived from calf thyroid (CTY), calf kidney (CK) and piglet kidney (PK) were immortalised by oncogene transfection and their susceptibility to infection by foot-and-mouth disease (FMD) virus and swine vesicular disease (SVD) virus examined. Eighty-five immortalised cell lines (47 CTY, 20 CK and 18 PK) proved stable upon repeated cell culture passage and many supported the growth of FMD virus and several of the PK cell lines supported SVD virus. However, none of the immortalised lines exhibited either the degree of sensitivity or the specificity for all virus serotypes and strains as shown by primary CTY and IB-RS-2 cell cultures which are routinely employed for vesicular virus diagnosis.

Warthog (Phacochoerus aethiopicus), giant forest hog (Hylochoerus meinertzhageni) and bushpig (Potamochoerus porcus) are known to be susceptible to infection with African swine fever (ASF) virus. Little however, is known about the ecology of the disease in the bushpig. This study has shown that the bushpig remains viraemic for between 35 and 91 days following infection during which time it is able to infect the tick vector O. moubata. These ticks were able to transmit the disease to pigs. The virus persists in the lymphatic tissues for less than 34 weeks. Bushpigs infected with LIL 20/l virus but not VIC T90/l virus transmitted infection to in-contact pigs. Infected domestic pigs did not transmit the infection to in-contact bushpigs. ASF virus was able to replicate in in vitro cultures of bushpig leucocytes and endothelial cells. Recovered bushpigs could be reinfected with some strains of virus but not others. While it has been demonstrated that bushpigs remain carriers of ASFV following infection a complete understanding of their significance in the epidemiology of the disease awaits further investigations of their association with O. moubata.