Ross River Virus: Ecology and Distribution

Abstract

Ross River virus is the most common mosquito-borne pathogen in Australia, and approximately 5000 human cases are reported annually. The infection is not fatal, but there is considerable morbidity associated with a debilitating polyarthritis that is the major symptom. The virus is annually active in most regions of Australia, but exists as strains that vary in virulence. Native macropods are thought to be the natural vertebrate hosts, although horses and humans may be involved during epidemic activity, and vertical transmission of the virus occurs in mosquitoes. Different mosquito species are involved as vectors in various regions and in different seasonal and environmental conditions. In coastal areas the saltmarsh mosquitoes Aedes camptorhynchus and Ae. vigilax are the most important vectors in southern and northern regions, respectively, whereas in inland areas Culex annulirostris is the most important vector, although various Aedes species can be involved depending on region and conditions, and the epidemiology of the disease and vector control imperatives vary with circumstance concomitantly.

Is New Zealand prepared to deal with arboviral diseases?

“…12 This can be a debilitating illness whose symptoms may persist for months or years. 3 There are a few mosquito species implicated in the transmission of RRV in Australia and, in coastal regions, one of the main vectors of the virus is the southern salt marsh mosquito Oc. camptorhynchus.…”

“…camptorhynchus. 3 Ochlerotatus camptorhynchus was first discovered in New Zealand, near Napier, in 1998. 13 It has since spread north from there to other areas, such as Kaipara Harbour.…”

“…They could serve as major amplifying hosts of local transmission of RRV, since macropods are the primary v ertebrate hosts of RRV in Australia. 3 Dama wallabies (Macropus eugenii) have steadily increased their distribution in the central North Island and Bay of Plenty since the 1940s and are now spread over at least 170,000 hectares. 28 According to the Department of Conser vation, this population is expanding and may now occupy an area as large as 500,000 ha.…”

“…For instance, in many Australian communities where RRV is an endemic problem, there are no routine vector control programs despite the high annual incidence of the disease. 3 However, apathy else where should not be adopted as the model for New Zealand.…”

“…2 Ross River virus (RRV; family Togaviridae, genus Alphavirus) is the most common mosquito-borne pathogen affecting humans in Australia, annually causing at least 5,000 illnesses. 3 An outbreak of infections with RRV seems likely to occur, at some time, sooner rather than later in New Zealand, 4,5 the likelihood having greatly increased since the discover y of the southern salt marsh mosquito Ochlerotatus (Ochlerotatus) camptorhynchus (Thomson) in the country. 6 Other arboviruses also pose potential threats to public health in New Zealand, particularly the dengue viruses (family Flaviviridae, genus Flavivirus) 7 .…”