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The problem of arbovirus infections in Maghreb has been relatively neglected in the pst in spite of a rich diversity of biotopes, the presence of potential reservoirs and vectors, and their position on the flight path of the Palearctic-african bird migration systems, western branch. Moreover, West Nile virus has been isolated from southern Algeria since 1968. From 1979 to 1989, ticks were collected from wild birds, pigeons, bats, rodents, poultry, camels, wild boars, domestic mammals and man, and assayed for viruses. On the whole, 424 ticks were virologically studied from Morocco, 582 from Algeria and 601 from Tunisia. Four tick-borne arboviruses have been isolated so far: three from Morocco, Soldado (Nairovirus), Essaouria (Orbivirus) and Kala Iris (Orbivirus) from Ornithodoros (A.) maritimus ticks parasitizing marine birds, and one from Tunisia, Tunis (Phlebovirus), from Argas reflexus hermanni infesting domestic pigeons. Soldado virus may infect man working into colonies of gulls for ornithological or entomological purposes and this infection is associated with a self-limited febrile illness and pruritus. In addition, antibody to Essaouira virus was detected in a wild rodent in Morocco. On the contrary it is unlike that Tunis virus may infect man because A. r. hermanni is a strickly ornithophilic tick. However, Uukuniemi group antibody has been previously evidenced in wild rodents in Tunisia. Finally, it is not excluded that other, more pathogenic, arboviruses such as Congo-Crimean haemorrhagic fever might be accidentally introduced in this sensitive geographical area.

Essaouira and Kala Iris viruses were isolated from Ornithodoros (Alectorobius) maritimus ticks parasitizing yellow-legged gulls (Larus cachinnans) on the coast of Morocco in 1979 and 1981, respectively. Serological evidence indicates that these two viruses are new members of the Chenuda complex within the Kemerovo serogroup of the genus Orbivirus. Ecological, pathological, morphological, and physicochemical properties are compatible with these findings. The infectivity of these viruses for man and animals, including seabirds, remains unknown.

Sera of 128 small wild mammals (rodents, insectivora) trapped in Northern Morocco in March 1979, were studied for antibody against 15 arboviruses. In inhibition-haemagglutination tests, positive reactions were found against West Nile (0.8%), Tahyna (21 %), Arumowot (14 %) and Sicilian Sandfly fever (9.4 %) viruses. In complement fixation tests, an unique serum from Apodemus sylvaticus was simultaneously positive for Quaranfil virus and for a Kemerovo group virus, Brest/Ar/T222, previously isolated from Ornithodoros (A.) maritimus ticks caught in Morocco. These results are discussed according to the bioclimatic profile of the station where the mammals originated and to the potential vectors known to occur here.

Pathogenicity of Soldado virus was clearly established in the past for seabirds but remained questionable for man. In a scientist, repeatedly bitten by Ornithodoros (A.) maritimus larvae at Essaouira (Morocco), the association of fever of unknown origin and of neutralizing antibody against an antigenic variant of Soldado virus isolated from the same place, lead to the conclusion that this virus may act as a pathogen for man. Epidemiological implications of such an observation are briefly discussed.