Import risk analysis: Llamas (Lama glama) and alpacas (Vicugna ...

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9. Bovine viral diarrhoea virus 9.1. HAZARD IDENTIFICATION 9.1.1. Aetiological agent Family: Flaviviridae; Genus: Pestivirus, Species: Bovine viral diarrhea virus (Thiel et al 2005). There are two genotypes BVDV1 and BVDV2 (Booth et al 1995). In each genotype both cytopathic and non-cytopathic biotypes occur. 9.1.2. OIE list Listed. However, it is not covered by a chapter in the Code. 9.1.3. New Zealand status Bovine viral diarrhoea virus genotype 1 (BVDV1) is endemic in New Zealand but genotype 2 (BVDV2) is exotic ( Vilcek et al 1998; Horner 2000). 9.1.4. Epidemiology BVDV1 has a world-wide distribution, including New Zealand and Australia (Horner 2000; Vilcek et al 1998). In New Zealand, most cattle have been exposed to BVDV1 and the prevalence of antibodies is around 60 % (Littlejohns & Horner 1990). BVDV2 occurs in North America (Potgieter 2004), Italy (Falcone et al 2001), the Netherlands (Barkema et al 2001) and in the United Kingdom (David et al 1994; Barkema et al 2001; Drew et al 2002; Nettleton & Gunn 2002; Cranwell et al 2005). The only isolation of a BVDV2 strain in New Zealand was from a batch of foetal calf serum imported from the USA (Horner 2000). The virus was contained in the laboratory. BVDV2 has not been described in Australia. BVDV is normally transmitted by direct contact between infected animals and/or possibly by aerosol transmission over short distances (Potgieter 2004). It is also transmitted in semen, particularly from persistently infected bulls which shed virus in their semen for years (Potgieter 2004). In cattle, the incubation period is usually about 3-7 days (Brownlie 2005) and the animals may remain viraemic for 4-15 days after initial infection (Potgieter 2004). Viraemia seldom exceeds 10-14 days (Brownlie 2005). Antibodies develop 2-4 weeks after infection. The incubation period and viraemic period of natural infections in camelids is not known. It is assumed that they are likely to be similar to those in cattle infections. BVDV1 infection of non-pregnant cattle usually results in a mild infection typified by pyrexia and leukopenia from about 3-7 days, with viraemia and nasal excretion of the virus occurring during this period (Brownlie 2005). The clinical signs are often so mild that they are not observed or only mild signs and occasionally diarrhoea is seen (Potgieter 2004). Since BVDV1 is widely distributed in most herds, cattle are commonly infected before they become pregnant, resulting in a population that is mostly immune and does not carry the virus. Infection of naïve pregnant animals, particularly during the first trimester, may result in death of the conceptus or full term, or near full term, delivery of immunotolerant persistently infected calves. 24 ● Import risk analysis: Llamas and alpacas from specified countries MAF Biosecurity New Zealand
It has been suggested that as many as 7 % of foetal deaths in Swiss dairy cattle may be caused by infection with BVDV (Rufenacht et al 2001). BVDV2 strains that cause a more severe form of the disease have been described in the USA (Pellerin et al 1994). In these cases the mortality rate was up to 10 % (Potgieter 2004) and the disease was characterised by severe leucopenia and haemorrhagic disease (Brownlie 2005). Immunotolerant persistently infected cattle may be clinically normal or may not thrive and die within a year. They are always infected with non-cytopathic strains of the virus (Brownlie 2005). Superinfection of persistently infected animals with a cytopathic BVDV strain results in the development of mucosal disease (MD) (Potgieter 2004; Brownlie 2005). The cytopathic strain that re-infects the persistent carrier animals may result from a mutation of the persistent non-cytopathic strain or from infection with a new extrinsic cytopathic virus (Potgieter 2004; Brownlie 2005). Mucosal disease is invariably fatal. In acute cases death occurs within 2-21 days while in chronic cases the animal may survive for up to 18 months (Potgieter 2004). An ELISA is available to detect BVDV antibody (Drew 2008). Despite the fact that serologically positive animals are usually no longer infected, exceptions are known to occur and a minority of persistently infected animals are also serologically positive. Some bulls that develop antibody titres continued to excrete infectious virus in semen for at least 5 months after experimental infection (Givens et al 2003). Further, a single case of a bull that was serologically positive and had no detectable virus in its blood but consistently excreted virus in its semen (Voges et al 1998). This led to a change in the recommendations made in the Code. It is now necessary for bulls that are antibody positive when they enter an AI station to have their semen tested for virus and for bulls that seroconvert to have every batch of semen that they have produced since their last negative serological test, tested for BVDV. It is assumed that male camelids could similarly be persistently infected although seropositive when imported. The antibody ELISA will not detect persistently infected animals that are immunotolerant. Antigen detection ELISAs are available but less sensitive than the RT-PCR. Although there is no Code chapter for BVDV, the Manual lists virus isolation or antigen-detection ELISA as the prescribed tests for international trade. An RT- PCR is available to detect viral RNA in blood (Rufenacht et al 2001; Stokstad et al 2003). Kapil et al (2009) state that the commercial antigen ELISA can give false positive results when testing camelid serum. He notes “screening new world camelids by BVD viralspecific PCR on whole blood will detect active infection/viraemia”, although PCR testing is not validated for international trade. BVD and MD are primarily diseases of cattle. Historical reports describe several serological studies that confirm camelids are susceptible to infection with BVDV. In a serological survey conducted in Peru on 117 alpacas that grazed with cattle, the prevalence of antibodies to BVDV was 11 %. In 270 llamas from Oregon, USA, the seroprevalence was reported to be 4.4 % (Wernery & Kaaden 2002). A survey of crias (unweaned baby camelids) in the USA found that 25 % of the herds studied were seropositive to BVDV (Topliff et al 2009). Historically, disease caused by BVDV in camelids had been described only once, in 1994. The affected llamas suffered excessive nasal discharge and diarrhoea before death. Experimental infection of four pregnant llamas during gestation did not result in clinical signs of disease or foetal infection or persistent BVDV infection of crias (Wentz et al 2003). MAF Biosecurity New Zealand Import risk analysis: Llamas and alpacas from specified countries ● 25
Page 1 and 2: Import risk analysis: Llamas (Lama
Page 3 and 4: MAF Biosecurity New Zealand Pastora
Page 5 and 6: CONTENTS Executive Summary 1 1. Int
Page 7 and 8: Acronyms CDC United States Centers
Page 9 and 10: Executive Summary This risk analysi
Page 11 and 12: 1. Introduction The importation of
Page 13 and 14: Figure 1. The risk analysis process
Page 15 and 16: Following public consultation on th
Page 17 and 18: Disease agent Foot and mouth diseas
Page 19 and 20: Disease agent PROTOZOA Eimeria alpa
Page 21 and 22: Bacteria, rickettsias and spirochae
Page 23 and 24: McKenna PB (2009). An updated check
Page 25 and 26: 6. African horse sickness virus 6.1
Page 27 and 28: 7. Bluetongue virus 7.1. HAZARD IDE
Page 29 and 30: 8. Borna virus 8.1. HAZARD IDENTIFI
Page 31: 8.2.2. Risk estimation Since entry
Page 35 and 36: Therefore, since the the consequenc
Page 37 and 38: Givens MD, Heath AM, Brock KV, Brod
Page 39 and 40: 10. Bovine herpesvirus type 1 10.1.
Page 41 and 42: 10.2.2. Exposure assessment Importe
Page 43 and 44: Bartha A, Haidu G, Aldassy P, Paczo
Page 45 and 46: 11. Epizootic haemorrhagic disease
Page 47 and 48: 12. Eastern equine encephalitis vir
Page 49 and 50: 13. Equine herpesvirus type 1 13.1.
Page 51 and 52: 13.2.2. Exposure assessment Assumin
Page 53 and 54: Davison AJ, Erberle R, Hayward GS,
Page 55 and 56: 1993). According to Fowler (1992),
Page 57 and 58: Veterinary Authorities should requi
Page 59 and 60: 15. Louping-ill virus 15.1. HAZARD
Page 61 and 62: 16. Rabies virus 16.1. HAZARD IDENT
Page 63 and 64: � Rabies is a serious zoonotic di
Page 65 and 66: 17. Vesicular stomatitis virus 17.1
Page 67 and 68: incubation period of the disease. T
Page 69 and 70: quarantined with protection from in
Page 71 and 72: Pharo HJ (1999). Vesicular stomatit
Page 73 and 74: 18.1.5. Hazard identification concl
Page 75 and 76: necessarily be competent vectors, a
Page 77 and 78: 20. Bacillus anthracis 20.1. HAZARD
Page 79 and 80: 20.3. RISK MANAGEMENT 20.3.1. Optio
Page 81 and 82: 21. Brucella spp. 21.1. HAZARD IDEN
Page 83 and 84:
21.2.4. Risk estimation Since entry
Page 85 and 86:
Gilsdorf MJ, Thoen CO, Temple RM, G
Page 87 and 88:
References References marked * were
Page 89 and 90:
Serological tests include the compl
Page 91 and 92:
with negative results using the com
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24. Coxiella burnetii 24.1. HAZARD
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� Although quarantine is not suit
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25. Leptospira serovars 25.1. HAZAR
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immune response is a low titre that
Page 101 and 102:
Retention of this empty Chapter, wi
Page 103 and 104:
26. Mycobacterium bovis 26.1. HAZAR
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26.3. RISK MANAGEMENT 26.3.1. Optio
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Page 109 and 110:
without any measures for detecting
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Animals become septicaemic a few ho
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29. Salmonella spp. 29.1. HAZARD ID
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animals and sporadic cases of salmo
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Hansen KR, Nielsen LR, Lind P (2006
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Camelidae diseases, or as transmitt
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32. Trypanosoma spp. 32.1. HAZARD I
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T. evansi and T. vivax occur in Sou
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5. Animals to be imported could be
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(Kittelberger et al 2002) and is th
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� The role of an IHS is to specif
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34. Internal parasites 34.1. HAZARD
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34.1.4.2. Trematodes The following
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34.2.4. Risk estimation Since entry
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35. Mites, lice and fleas 35.1. HAZ
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35.2. RISK ASSESSMENT 35.2.1. Entry
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N.B. This measure reflects the curr
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Hard ticks (Ixodidae) have a lifecy
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1. Camelids could be treated with p
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the Eastern Cape and North-West Pro
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The larvae reach maturity about 4-8
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exploration, debriding and flushing
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a. all animals have been re-examine
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38. Weeds and seeds 38.1. HAZARD ID
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edding materials include wood shavi
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