Equine infectious anaemia in Europe: Time to re-examine the efficacy of monitoring and control protocols?

Equine infectious anaemia (EIA) is a disease with an almost worldwide distribution and is of considerable importance to the equine industry, primarily because it is one of only 11 notifiable equine specific diseases listed by the World Organisation For Animal Health (OIE). Equine infectious anaemia is caused by EIAV (equine infectious anaemia virus), a blood-borne retrovirus belonging to the lentivirus genus [1]. It is unfortunate that the disease only receives significant attention when an EIA outbreak has a significant financial impact [2]. Equine infectious anaemia outbreaks have been reported in Belgium, Bosnia, Croatia, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Romania, Serbia, Slovenia and the UK between 2007 and 2014 [3]. In countries where EIA re-emerged after several years of absence such as in Belgium, Germany, Ireland and the UK, epidemiological studies suggested that equine biological products (such as blood plasma) imported from Italy or Romania were the source of the outbreaks. Moreover, several European countries (including Hungary, Poland and Serbia) have recently reported new EIA outbreaks and cases, underlining a wider extent of the disease in Europe than previously reported. Recent outbreaks of EIA in European Union (EU) countries have prompted a closer look at the disease and alternative routes of transmission. Traditionally, EIA is seen as a blood-borne disease that can be mechanically transmitted by various blood-feeding insects, mainly Tabanidae. However, human actions (either iatrogenic or not) are suggested to have been an important contributory element, especially in recent outbreaks like the one in Ireland in 2006 [4]. In at least some of the EIA cases in the Irish outbreak (16 out of 38), it has been hypothesised that infection might have occurred through aerosolisation of infectious particles as a result of cleaning with pressure washers [5]. A few European nations reported EIA to the OIE between 2013 and 2014, namely Bosnia, Croatia, Hungary, Italy, Latvia, Romania and Serbia [3]. Two of these countries had ongoing (Romania) or have initiated (Italy in 2007) active surveillance programmes for EIA including systematic yearly testing of equids. Equine infectious anaemia is reported as endemic in the 2 EU countries that use systematic serological testing (Italy and Romania). We recently performed an 18 year retrospective study in Romania comparing the numbers of reported EIA outbreaks, number of individual cases and number of seropositive equids subjected to euthanasia as a result of the diagnosis. The data was collected from the OIE’s World Animal Health Information System (WAHIS for information after 2005) and Handistatus II (for information prior to 2005) and from the Institute for Diagnosis and Animal Health (IDAH), Bucharest, Romania. It is important to note that the Italian National Surveillance Programme that ran between 2007 and 2011 [6,7] demonstrated that testing exclusively using agar gel immunodiffusion (AGID), (the OIE prescribed test) can yield false negative results from a sizeable proportion of EIAV infected equids (perhaps exceeding 20%), thus emphasising the necessity to combine AGID with more sensitive tests such as ELISA or immunoblotting for more accurate detection and diagnosis.