NATIONAL ARBOVIRUS MONITORING PROGRAM NAMP REPORT

Transcription

1 NATIONAL ARBOVIRUS MONITORING PROGRAM NAMP REPORT Report on the rbovirus trnsmission seson (September 2016 to August 2017) OBJECTIVES OF THE NATIONAL ARBOVIRUS MONITORING PROGRAM The Ntionl Arbovirus Monitoring Progrm (NAMP) hs three specific objectives: mrket ccess to fcilitte the export of live 1 cttle, sheep nd gots, nd ruminnt genetic mteril, to countries with concerns bout bluetongue, Akbne nd bovine ephemerl fever (BEF) viruses. bluetongue erly wrning to detect 2 incursions of exotic strins of bluetongue virus (BTV) nd vectors (Culicoides species biting midges) into Austrli by surveillnce of the northern BTV-endemic re. risk mngement to detect chnges in the 3 sesonl distribution in Austrli of endemic bluetongue, Akbne nd BEF viruses nd their vectors, to support livestock exporters nd producers. The NAMP mngement, prtners nd coordintors would like to thnk everyone who ssisted in gthering the vluble monitoring dt tht underpin this report. This ssistnce is criticl in mintining nd developing mrket ccess. NAMP monitors the distribution of economiclly importnt rboviruses (insect-borne viruses) of ruminnt livestock nd ssocited insect vectors in Austrli. Arboviruses monitored by NAMP include bluetongue, Akbne nd BEF viruses. BTV infection does not dversely ffect production in Austrlin livestock, nd disese hs not been reported from res of known virl trnsmission. Austrli s economy benefits from the export of ruminnt livestock nd their genetic mteril (semen nd embryos). This trde depends on shred confidence between Austrli nd its trding prtners tht risks to the niml helth sttus of the importing country cn be ccurtely ssessed nd properly mnged. NAMP provides credible dt on the nture nd distribution of importnt specific rbovirus infections in Austrli for use by the Austrlin Government nd livestock exporters. NAMP underpins Austrlin Government export certifiction tht Austrlin ruminnts re sourced from res tht re free from trnsmission of these specified rboviruses. In ddition, NAMP dt re vilble for other countries when negotiting their import helth conditions for Austrlin livestock nd their genetic mteril. NAMP is jointly funded by its primry beneficiries: the cttle, sheep nd got industries; the livestock export industry; nd the stte, territory nd Austrlin governments. OPERATION OF THE NATIONAL ARBOVIRUS MONITORING PROGRAM NAMP dt re gthered throughout Austrli by serologicl monitoring of cttle in sentinel herds, strtegic serologicl surveys of other cttle herds (serosurveys), nd trpping of insect vectors. Blood smples from groups of young cttle tht hve not previously been exposed to rbovirus infection re tested t regulr intervls for evidence of new infection with the bluetongue, Akbne nd BEF viruses. The frequency of blood smpling reltes to the probbility of rbovirus 1

2 trnsmission tht is, the greter the likelihood of virl trnsmission, the more frequent the smpling. Insect trps to detect Culicoides species re positioned ner the monitored herds during the period of testing or ner herds where conditions re fvourble for Culicoides species survivl. The number nd loctions of herds (Figure 1) re selected to enble the distribution of the specified rboviruses to be determined (e.g. sentinel sites locted long the border between the zone where infection is expected nd not expected, nd sentinel sites in res where infection occurs spordiclly), nd the rbovirus-free re is monitored to verify freedom. Known endemiclly infected res re smpled to detect ny new strins of virus nd to ssess the sesonl intensity of infection with ech rbovirus. Betrice Hill in the fr north of the Northern Territory is focus for exotic BTV surveillnce; virus isoltion is routinely undertken on blood smples collected t this loction. Serotyping, virus isoltion nd moleculr testing re pplied strtegiclly in other herds in New South Wles, Northern Territory, Queenslnd nd Western Austrli fter seroconversions re detected. NAMP surveillnce dt relting to bluetongue erly wrning re supplemented by trgeted surveillnce ctivities conducted by the Northern Austrli Qurntine Strtegy of the Austrlin Government Deprtment of Agriculture nd Wter Resources in remote costl regions of northern Austrli, including the Torres Strit Islnds. EPIDEMIOLOGY Bluetongue, Akbne nd BEF viruses re noncontgious nd re biologiclly trnsmitted by their insect vectors. Climtic fctors (rinfll nd temperture) determine the distribution of potentil vectors. The rboviruses re trnsmitted only if vectors re present in sufficient density. Culicoides brevitrsis is the min vector of both BTV nd Akbne virus. A close correltion exists between the southern limits of C. brevitrsis nd the distribution of the two viruses, lthough the viruses re less widely distributed thn their vectors. Other vectors of BTV in Austrli which re less widely distributed thn C. brevitrsis, re C. ctoni, C. dumdumi, C. fulvus nd C. wdi. The min vector of BEF virus in Austrli is generlly considered to be the mosquito Culex nnulirostris. C. nnulirostris hs different ecologicl thresholds from C. brevitrsis, prticulrly its tolernce to lower tempertures, which ccounts for its wider distribution nd its occurrence in regions not ffected by BTV or Akbne virus. Reserch in Austrli since the mid-1970s hs provided detiled understnding of the epidemiology of Austrlin BTV strins nd their Culicoides midge Figure 1 Loctions of Ntionl Arbovirus Monitoring Progrm virology monitoring sites, rbovirus trnsmission seson Desert Tropicl Equtoril Stte Borders Grsslnd Sub-tropicl Temperte Alpine Köppen climte clssifiction 2

3 vectors. The importnt vector species in Austrli re likely to hve ll originlly rrived on ir currents from neighbouring countries. Mny regions in Austrli hve never recorded the presence of competent Culicoides vectors nd re therefore free from virl trnsmission of rboviruses tht cn only be spred by these vector species (BTV nd Akbne virus). BEF, which is primrily spred by certin species of mosquito, hs more vrible distribution, prticulrly in southern Austrli. Climtic conditions hve significnt effect on vector distribution nd prtly ccount for chnges tht occur to the boundry between res where virl trnsmission occurs nd res free of trnsmission. MONITORING RESULTS FOR This section summrises nd explins the results of vector nd virus monitoring nd describes the limits of distribution of the bluetongue, Akbne nd BEF viruses in the rbovirus trnsmission seson (September 2016 to August 2017). The numbers of monitoring sites for smple collection in ech stte nd territory re shown in Tble 1. Tble 1 Number of NAMP virology monitoring sites, by stte nd territory, Jurisdictions New South Wles Northern Territory Sentinel herds Serosurveys Insect trps Queenslnd South Austrli Tsmni Victori Western Austrli TOTAL BLUETONGUE VIRUS DISTRIBUTION The limits of BTV trnsmission in Austrli re shown on the interctive Bluetongue Virus Zone Mp, 1 which defines res in which no virl trnsmission 2 hs been detected for the pst two yers. BTV trnsmission is endemic in northern nd northestern Austrli (New South Wles, Northern Territory, Queenslnd nd Western Austrli), nd remins undetected in South Austrli, Tsmni nd Victori (Figure 2). No new serotypes were detected in Austrli during. During the months leding up to the monsoon seson, the Northern Territory recorded higher tempertures thn verge nd severe thunderstorms in November. The first hlf of December ws very dry cross ll prts of the Northern Territory except the fr south. These dry conditions were broken by multiple monsoons until April. As result, Drwin s wet seson rinfll totl ws its third-highest on record. Virologicl testing in the Northern Territory showed tht BTV trnsmission ws very widespred, commencing 1 nmp.nimlhelthustrli.com.u 2 Virl trnsmission is defined s detection of evidence of virl infection bsed on serologicl monitoring of cttle. in October in ll the northern herds nd continuing through until June. Serotype BTV16 ws detected t four of the northernmost sentinel sites nd BTV1 t ll the northern sites. BTV5 nd BTV21 were lso found lte in the seson t three of the northern sites. Virus ws isolted from monitoring conducted throughout the yer t Betrice Hill every month except August nd September. Serosurveys identified BTV16 ntibody t Wve Hill in the Victori River District nd Kurundi south of Tennnt Creek. This lst detection ws responsible for southern extension of the BTV zone in June In Western Austrli, bove verge rinfll nd higher winter tempertures were recorded in the Kimberley nd estern Pilbr. These conditions nd the recently estblished irrigtion crops my increse vector survivl. Sentinel site follow-up smple collections were delyed until these properties could muster stock, but were completed by August BTV seroconversions hve been reported t ll NAMP sites within the Kimberley BTV zone except the southwestern sites of Livering nd Broome Common. The predominnt serotypes identified with virus neutrlistion test for this seson hve been BTV1 nd BTV21 with some evidence of exposure to BTV16 t two serosurvey sites, possibly indictive of the seson seroconversions. A positive pre- 3

4 BTV21). This is the first occsion tht BTV16 hs been detected in New South Wles (lthough retrospective testing hs determined it ws first present on the Fr North Cost of New South Wles in April 2016). BTV1 nd BTV21 were detected in ll the sentinel herds long the costl plin to the Sydney Bsin, with mixed infections detected in mny nimls. In the Hunter Vlley, BTV1, BTV16 nd BTV21 were ll detected. export test result from cttle from property in the BTV surveillnce zone led to n investigtion on the property. This confirmed evidence of BTV trnsmission on the property nd n expnsion of the BTV trnsmission nd surveillnce zone ws instigted. The expnsion notbly included the Broome port, the mjor export depot yrds nd holding properties in Broome nd the current Broome cttle tick dipping yrds. No evidence of BTV trnsmission ws detected south of the Kimberley in Western Austrli. BTV16 ws not detected t ny intervening sites on the New South Wles cost or rnges between the most southern point of detection in Queenslnd nd the New South Wles Hunter Vlley. This loclised detection of BTV16 my be relted to niml movements or perhps consequence of Cyclone Debbie. Numbers of C. brevitrsis were significntly higher thn ever previously recorded t Pterson in the Hunter Vlley in the month before the detection of BTV (including BTV16) in the region. BTV ctivity ws consistent with the distribution of C. brevitrsis. Culicoides wdi ws detected cross wider geogrphicl distribution nd in greter numbers thn in ny previous seson, but it ws restricted to the north cost nd ws not ssocited with the detection of BTV16. In Queenslnd, during spring, the western, centrl nd southern prts experienced bove-verge rinfll. Below-verge flls were recorded in the fr north, with record men dily mximum tempertures experienced t some loctions. High men tempertures were recorded in both summer nd utumn, with mixed rinfll pttern. Cyclone Debbie cused flooding nd dmging winds in centrl nd south-estern res. In winter there ws little rin, with some loctions experiencing the driest June on record, but overll men mximum tempertures were bove verge. BTV16 ws discovered in Cooktown, Normnton, Mryborough, Chinchill, Mcky nd Allor, which is close to the New South Wles border. BTV1 ws lso detected in northern, centrl nd southern Queenslnd, with mix of BTV21. In Victori, winter nd spring rinfll ws bove verge cross the whole stte. Hevy spring rinfll led to flooding in some res, resulting in very high mosquito numbers. Tempertures were slightly bove verge in winter nd close to verge in spring. Summer verge dytime tempertures were bove verge in most prts of Victori, but totl rinfll ws below verge. Autumn ws wrmer thn usul nd, lthough rinfll ws round verge for the seson, June ws very dry for lmost ll of the stte. No BTV ctivity ws detected t ny of the four sentinel herd sites or the one serosurvey site in Victori during the seson. In New South Wles, rinfll cross the endemic zone for BTV ws verge to below verge for much of the trnsmission seson except for very much bove verge to highest on record rinfll in lte Mrch fter Cyclone Debbie. BTV seroconversions were first detected this seson on the mid-north cost during Jnury, lter extending to the Fr North Cost, upper Hunter Vlley, Sydney Bsin, South Cost nd NorthWest Slopes regions. This widespred trnsmission pttern resulted in expnsions of the BTV zone in four regions this seson. No competent vector species were detected in South Austrli, Tsmni or Victori, consistent with the serologicl evidence of virus bsence. This yer ws unique in tht three serotypes of BTV were detected in New South Wles (BTV1, BTV16 nd Figure 2 Distribution of bluetongue virus in Austrli, to Bluetongue virus distribution Köppen climte clssifiction 4 Bluetongue virus free res Desert

5 AKABANE VIRUS DISTRIBUTION The distribution of Akbne virus (Figure 3) vries within the limits of its vector, C. brevitrsis, occurring endemiclly in northern Austrli (northern Queenslnd, Northern Territory nd Western Austrli) nd showing distinct sesonl spred in New South Wles nd southern prts of Queenslnd. Microscopy imge of Culicoides midge wing used for species identifiction In Western Austrli, Akbne seroconversions hve been detected on ll the Kimberley NAMP sites. However, there hs been no evidence of Akbne trnsmission in the Pilbr or southwest of Western Austrli. In the Northern Territory, no Akbne testing ws performed in the northern endemic herds nd no ctivity ws detected t Alice Springs. In New South Wles, Akbne virus trnsmission ws more extensive thn BTV nd ws lso detected in the Northern Tblelnds nd Fr South Cost regions, which re not considered endemic for this virus. Its distribution ws mostly consistent with this seson s distribution of the vector C. brevitrsis. There hve been confirmed cses of Akbne-ffected clves on the Northern Tblelnds. In Queenslnd, seroconversion t sentinel sites nd seropositive nimls recorded t survey sites were brodly distributed cross ll regions. Generlly, only first nd lst smples were tested t sentinel sites. Figure 3 Distribution of Akbne virus in Austrli, to Akbne virus remins undetected in South Austrli, Tsmni nd Victori Akbne virus distribution Akbne virus free res Desert Köppen climte clssifiction BOVINE EPHEMERAL FEVER VIRUS DISTRIBUTION risk of BEF in disese investigtion of downer cttle in n export depot. Lbortory testing confirmed tht BEF ws not the cuse. In the Northern Territory, BEF ctivity ws comprtively reduced compred to most yers, with the only significnt ctivities being in some northern loctions. BEF virus is endemic in northern Austrli (Northern Territory, Queenslnd nd Western Austrli), where fever cn occur in both the dry nd wet sesons (spring, summer or utumn). In New South Wles nd prts of southern Queenslnd, occurrence of the virus is limited by the effect of cold winters, restricting the distribution of its mosquito vector (Figure 4). In Western Austrli, BEF seroconversions hve been found t the two sentinel sites in the Kimberley. This distribution ws reduced from previous yers nd, s expected, no signs of clinicl disese were reported. The other sites hve been negtive for BEF this seson. Informtion from NAMP helped ssess the Microscopy imge of Culicoides midge hed used for species identifiction 5

6 In Queenslnd, BEF virus ws gin detected widely cross the stte, extending to the fr south-est nd fr south-west. northern nd centrl New South Wles my provide optiml conditions for n epizootic of BEF in inlnd New South Wles if wet conditions persisted through into summer. Cses were only confirmed from midsummer to erly utumn on the fr to mid-north cost. In New South Wles, BEF virus ctivity ws not detected in ny of the monitored sentinel herds in inlnd New South Wles nd south cost regions. This ws despite erly seson concerns tht significnt rinfll nd flooding during August nd September in Figure 4 Distribution of bovine ephemerl fever virus in Austrli, to BEF virus ws not detected in South Austrli, Tsmni or Victori Bovine ephemerl fever virus distribution Bovine ephemerl fever virus free res Desert Köppen climte clssifiction CONTACT OFFICERS If you would like more informtion bout NAMP, plese contct the relevnt officer listed. Nme Orgnistion Number In Lngstff Animl Helth Austrli (Progrm Mnger) Andrew Moss Animl Biosecurity Brnch, Austrlin Government Deprtment of Agriculture nd Wter Resources Debbie Egles CSIRO Austrlin Animl Helth Lbortory Deborh Finlison New South Wles Deprtment of Primry Industries Lorn Melville Northern Territory Deprtment of Primry Industry nd Resources Bruce Hill Queenslnd Deprtment of Agriculture nd Fisheries Trent Scholz Deprtment of Primry Industries nd Regions South Austrli Debbie Grull Tsmnin Deprtment of Primry Industries, Prks, Wter nd Environment Kren Moore Victorin Deprtment of Economic Development, Jobs, Trnsport nd Resources Mrion Seymour Western Austrlin Deprtment of Primry Industries nd Regionl Development Beth Cookson Northern Austrli Qurntine Strtegy, Austrlin Government Deprtment of Agriculture nd Wter Resources Glenn Bellis Northern Austrli Qurntine Strtegy, Austrlin Government Deprtment of Agriculture nd Wter Resources Previous nnul reports re vilble from the Animl Helth Austrli website NAMP pge. ISBN ISSN Published Jnury 2018 Animl Helth Austrli Disclimer: This publiction is published by Animl Helth Austrli for informtion purposes only. Informtion contined in it is drwn from vriety of sources externl to Animl Helth Austrli. Although resonble cre ws tken in its preprtion, Animl Helth Austrli does not gurntee or wrrnt the ccurcy, relibility, completeness or currency of the informtion or its usefulness in chieving ny purpose. To the fullest extent permitted by lw, Animl Helth Austrli will not be lible for ny loss, dmge, cost or expense incurred in or rising by reson of ny person relying on the informtion in this publiction. Persons should ccordingly mke nd rely on their own ssessments nd enquiries to verify the ccurcy of the informtion provided. 6