Abstract: African Horsesickness (AHS) is a controlled disease in South Africa. The country is divided into an infected area and a control area. An outbreak of AHS in the control area can result in a ban of exports for at least 2 years. A retrospective epidemiological study was carried out on data collected during the 2004 AHS outbreak in the surveillance zone of the AHS control area in the Western Cape Province. The objective of this study was to describe the 2004 outbreak and compare it with the 1999 AHS outbreak in the same area. As part of the investigation, a questionnaire survey was conducted in the 30 km radius surrounding the index case. Spatial, temporal and population patterns for the outbreak are described. The investigation found that the outbreak occurred before any significant rainfall and that the main AHS vector (Culicoides imicola) was present in abundance during the outbreak. Furthermore, 63% of cases occurred at temperatures < or = 15 degrees C, the Eerste River Valley was a high risk area, only 17% of owners used vector protection as a control measure and 70% of horses in the outbreak area were protected by means of vaccination at the start of the outbreak. The study revealed that the current AHS control measures do not function optimally because of the high percentage of vaccinated horses in the surveillance zone, which results in insufficient sentinel animals and the consequent failure of the early warning system. Alternative options for control that allow continued export are discussed in the paper.

Abstract: Eastern equine encephalitis virus (EEE) was isolated from the salt marsh mosquito, Aedes sollicitans, collected from coastal areas of New Jersey on 3 occasions during the late summer and fall of 1982. The isolations were made at a time when local Culiseta melanura were either undergoing a population increase or exhibiting high levels of EEE virus. Although no human cases were reported during the epizootic period, the data lend support to the hypothesis that Ae. sollicitans is capable of functioning as an epidemic vector in the coastal areas of New Jersey where human cases of EEE have been most common.

Abstract: African horse sickness virus (AHSV) causes a non-contagious, infectious insect-borne disease of equids and is endemic in many areas of sub-Saharan Africa and possibly Yemen in the Arabian Peninsula. However, periodically the virus makes excursions beyond its endemic areas and has at times extended as far as India and Pakistan in the east and Spain and Portugal in the west. The vectors are certain species of Culicoides biting midge the most important of which is the Afro-Asiatic species C. imicola. This paper describes the effects that AHSV has on its equid hosts, aspects of its epidemiology, and present and future prospects for control. The distribution of AHSV seems to be governed by a number of factors including the efficiency of control measures, the presence or absence of a long term vertebrate reservoir and, most importantly, the prevalence and seasonal incidence of the major vector which is controlled by climate. However, with the advent of climate-change the major vector, C. imicola, has now significantly extended its range northwards to include much of Portugal, Spain, Italy and Greece and has even been recorded from southern Switzerland. Furthermore, in many of these new locations the insect is present and active throughout the entire year. With the related bluetongue virus, which utilises the same vector species of Culicoides this has, since 1998, precipitated the worst outbreaks of bluetongue disease ever recorded with the virus extending further north in Europe than ever before and apparently becoming endemic in that continent. The prospects for similar changes in the epidemiology and distribution of AHSV are discussed.

Abstract: African horse sickness (AHS) is an infectious but no-contagious viral disease of equidae with high mortality in horses. The disease is caused by an arthropod-borne double-stranded RNA virus within the genus Orbivirus of the family Reoviridae transmitted by at least two species of Culicoides. Nine different serotypes have been described. The nine serotypes of AHS have been described in eastern and southern Africa. Only AHS serotypes 9 and 4 have been found in West Africa from where they occasionally spread into countries surrounding the Mediterranean. Examples of outbreaks that have occurred outside Africa are: in the Middle East (1959-1963), in Spain (serotype 9, 1966, serotype 4, 1987-1990), and in Portugal (serotype 4, 1989) and Morocco (serotype 4, 1989-1991). Laboratory diagnosis of AHS is essential. Although the clinical signs and lesions are characteristic, they can be confused with those of other diseases. Several techniques have been adapted for the detection of RNA segments, antibodies and antigen. Two types of vaccines have been described for AHS virus. Attenuated live vaccines (monovalent and polyvalent) for use in horses, mules and donkeys, are currently available, as well as a monovalent, serotype 4, inactivated vaccine, produced commercially but no longer available. New vaccines, including a subunit vaccine, have been evaluated experimentally. In this paper a review of the last AHS outbreaks in Spain, occurring during 1987-1990, and affecting the central and south part of the country, is presented. The role that vaccination played for the control and eradication of the disease, as well as other aspects such as climatological conditions, number of vectors and horse management, are also presented and evaluated.

Abstract: The genus Thelazia (Spirurida, Thelaziidae) includes a cosmopolitan group of eyeworm spirurids responsible for ocular infections in domestic and wild animals and transmitted by different species of muscids. Bovine thelaziosis is caused by Thelazia rhodesi Desmarest 1828, Thelazia gulosa Railliet & Henry 1910, and Thelazia skrjabini Erschow 1928, which occur in many countries; T. gulosa and T. skrjabini have been reported mainly in the New World, while T. rhodesi is particularly common in the Old World. In Italy, T. rhodesi was reported in southern regions a long time ago and, recently, T. gulosa and T. skrjabini have been identified in autochthonous cattle first in Apulia and then in Sardinia. Thirteen species of Musca are listed as intermediate hosts of eyeworms, but only Musca autumnalis and Musca larvipara have been demonstrated to act as vectors of Thelazia in the ex-URSS, North America, ex-Czechoslovakia and more recently in Sweden. In Italy, after the reports of T. gulosa and T. skrjabini in southern regions, the intermediate hosts of bovine eyeworms were initially only suspected as the predominant secretophagous Muscidae collected from the periocular region of cattle with thelaziosis were the face flies, M. autumnalis and M. larvipara, followed by Musca osiris, Musca tempestiva and Musca domestica. The well-known constraints in the identification of immature eyeworms to species by fly dissection and also the time-consuming techniques used constitute important obstacles to epidemiological field studies (i.e. vector identification and/or role, prevalence and pattern of infection in flies, etc.). Molecular studies have recently permitted to further investigations into this area. A PCR-RFLP analysis of the ribosomal ITS-1 sequence was developed to differentiate the 3 species of Thelazia (i.e. T. gulosa, T. rhodesi and T. skrjabini) found in Italy, then a molecular epidemiological survey has recently been carried out in field conditions throughout five seasons of fly activity and has identified the role of M. autumnalis, M. larvipara, M. osiris and M. domestica as vectors of T. gulosa and of M. autumnalis and M. larvipara of T. rhodesi. Moreover, M. osiris was described, for the first time, to act as a vector of T. gulosa and M. larvipara of T. gulosa and T. rhodesi. The mean prevalence in the fly population examined was found to be 2.86%. The molecular techniques have opened new perspectives for further research on the ecology and epidemiology not only of Thelazia in cattle but also of other autochthonous species of Thelazia which have been also recorded in Italy, such as Thelazia callipaeda, which is responsible for human and canid ocular infection and Thelazia lacrymalis, the horse eyeworm whose epidemiological molecular studies are in progress.