Possible spread of African horse sickness on the wind

Abstract

SUMMARYAnalyses of outbreaks of African horse sickness showed that movement of infected Culicoides midges on the wind was most likely responsible for the spread of the disease over the sea from Morocco to Spain in 1966, from Turkey to Cyprus in 1960, and from Senegal to the Cape Verde Islands in 1943. The pattern of spread of the epidemic in the Middle East in 1960 could have been laid down by the infected midges carried on spells of south-east winds, and analyses of outbreaks in Algeria in 1965 and India in 1960 also suggested windborne spread of the disease. Each spread occurred when the presence of virus, host and vector coincided either with a spell of winds unusual for a particular time of year (Spain, Cyprus, Cape Verde Islands and Algeria) or with a series of disturbances usual at that time of the year (Middle East and India). Inferred flight endurance of the midge varied up to at least 20 h and flight range from 40 to 700 km. Flight occurred when temperatures were likely to have been in the range of 15–25 °C if it was at night or 20 to about 40 °C if it was by day.It is suggested that likely movements of midges on the wind can be estimated from synoptic weather charts, and should be taken into account when planning control of the disease in the face of an outbreak. Such control includes a ban on movement of horses, vaccination and spraying of insecticide.The risk of spread to countries outside the endemic areas should be assessed by reference to possible wind dispersal of infected midges.

CulicoidesBiting Midges: Their Role as Arbovirus Vectors

“…Before it was known even that BEFV is transmitted by Culicoides, Seddon (155) demonstrated that the spread of BEF in Australia was explainable by wind patterns. Subsequently, numerous studies have related the spread of Culicoides-borne viral diseases to wind movements (25, 28, 50, 66,115,124,127,137,158,159,160,162,163,164). In all cases the evidence is circumstantial, and alternative modes of introduction can rarely be ruled out.…”

Isolations of African horse sickness virus from vector insects made during the 1988 epizootic in Spain

“…However, at intervals the virus makes excursions beyond these enzootic zones to initiate epizootics ranging as far as India and Pakistan in the East [1], Turkey and Cyprus in the North [1,2] and Morocco and the Cape Verde Isles in the West [2]. The first recorded outbreak of AHS in Spain occurred in early October 1966 during an epizootic of type 9 AHSV which was centred in North Africa [3,4].…”

Detection of Low-Level Cardinium and Wolbachia Infections in Culicoides

“…Capable of wind-borne displacement for several hundred kilometers, Culicoides spp. have a capacity for rapid long-distance transmission of disease and have recently been responsible for the establishment of enzootic BTV and SBV infections over vast new geographic areas (1,2). Current control methods for Culicoides include breeding site removal and baiting of livestock and midge resting sites; however, these techniques are costly and labor-intensive and have various levels of success and permanence of control (3).…”