Review of the sylvatic cycle of African swine fever in sub-Saharan Africa and the Indian ocean

A frican swine fever (ASF) is a complex and lethal viral disease affecting swine and has a significant socioeconomic impact on both the developed and developing world. It has a major negative effect on national, regional, and international trade and constrains pig production in affected areas. The devastating acute form of the disease is characterized, among other features, by functional and congestive-hemorrhagic disorders of the digestive and respiratory systems and causes around 100% mortality in infected pigs (1). Both European wild boars (Sus scrofa) and feral pigs are susceptible and exhibit clinical signs and mortality rates similar to those of domestic pigs. In contrast, African wild pigs (Phacochoerus and Potamochoerus spp.) are resistant to the disease (2-10).The causative agent of the disease, the ASF virus (ASFV), is a large double-stranded DNA virus and the only member of the Asfarviridae family, genus Asfivirus (11, 12). The virus genome is 170 to 192 kb long (13-17). ASF is endemic in sub-Saharan Africa, where it was first described in 1921 (18). Several outbreaks have occurred since then in Europe and South and Central America. In most non-African countries, the disease has been successfully eradicated, the only exception being Sardinia (Italy), where the disease is still endemic (19,20). In April 2007, the disease spread from East Africa to the Republic of Georgia (21), and outbreaks occurred in Armenia, Azerbaijan, and the Russian Federation (22). The ongoing spread of ASFV into adjacent eastern European countries, such as Ukraine (23,24) and Belarus (25), and the situation in Russia affecting both wild boars and domestic pigs placed neighboring areas in the European Union (EU) at risk for the spread of ASFV. The first cases of ASF in wild boars in Lithuania and Poland were reported in early 2014 in areas bordering . According to the World Organisation for Animal Health (OIE), during 2014, nearly 260 ASF cases or outbreaks in wild boars and domestic pigs were detected in EU countries (Latvia, Lithuania, Estonia, and Poland). This situation, combined with the uncertainty present in Belarus, has created a permanent risk of reintroducing ASF into the EU via wild boars or the illegal trade of contaminated pork products and waste (31).No vaccine is available to prevent ASF infection. The control and eradication measures applicable are based on classical disease control methods, including surveillance, epidemiological investigation, tracing of pigs, and stamping out in infected holdings. Citation Gallardo C, Nieto R, Soler A, Pelayo V, Fernández-Pinero J, MarkowskaDaniel I, Pridotkas G, Nurmoja I, Granta R, Simón A, Pérez C, Martín E, Fernández-Pacheco P, Arias M. 2015. Assessment of African swine fever diagnostic techniques as a response to the epidemic outbreaks in eastern European Union countries: how to improve surveillance and control programs.

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“…In contrast, African wild pigs (Phacochoerus and Potamochoerus spp.) are resistant to the disease (2)(3)(4)(5)(6)(7)(8)(9)(10).…”

mentioning

confidence: 99%

Assessment of African Swine Fever Diagnostic Techniques as a Response to the Epidemic Outbreaks in Eastern European Union Countries: How To Improve Surveillance and Control Programs

et al. 2015

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“…ASFV is maintained through ticks Ornithodoros moubata and warthogs (Phacochoerus spp.) in sylvatic transmission cycle in Africa (Jori et al, 2012). In addition, some recent studies suggest that ticks may also play a role in the circulation of another DNA virus, Murid herpes virus 4, strain MHV-68 (Ficová et al, 2011;Hajnická et al, submitted).…”

Section: Tick-borne Virusesmentioning

confidence: 99%

Non-viraemic transmission of tick-borne viruses

Havlíková¹,

Ličková²,

Klempa³

2013

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Summary. -Tick-borne viruses are causative agents of several important human diseases. Tick-borne encephalitis virus (TBEV) is the most prominent representative considered medically to be the most important arbovirus (arthropod-borne virus) in Europe and northern Asia. Tick-borne virus transmission cycles are determined by the interactions between viruses, vectors, and their vertebrate hosts. Several mechanisms of tick-borne virus circulation in nature are currently considered to include transovarial transmission via the eggs from an infected female tick to its offspring, "viraemic" transmission between host and tick via feeding on a viraemic, infectious vertebrate hosts, and the virus transmission between co-feeding ticks, termed non-viraemic transmission (NVT). For NVT, the local skin site where ticks aggregately feed is an important focus of viral replication where migratory immune cells provide a vehicle for virus transmission from infected to uninfected co-feeding ticks. For TBEV at least, NVT is an important mechanism of virus maintenance in nature and offers explanations for some specific aspects of tick-borne virus ecology such as focal virus distribution and vector competency of particular tick species.Keywords: routes of transmission; non-viraemic transmission; arbovirus; tick-borne viruses; co-feeding; tick-borne encephalitis virus E-mail: virusaha@savba.sk; phone: +421-2-59302428. Abbreviations: ASFV = African swine fever virus; CCH-FV = Crimean-Congo hemorrhagic fever virus; NVT = nonviraemic transmission; SAT = saliva-activated transmission; SGE = salivary gland extract; THOV = Thogoto virus; TBEV = tickborne encephalitis virus

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“…It can have severe socio-economic impacts due to high mortality and trade restrictions [1]. ASF is considered the major limiting factor for pig production in many sub-Saharan African countries where a significant commercial pig industry exists [1, 2]. ASF has also spread outside Africa, including recently to the Caucasus and Russia, posing considerable threats to the global pig industry [3–6].…”

Section: Introductionmentioning

confidence: 99%

“…ASF has also spread outside Africa, including recently to the Caucasus and Russia, posing considerable threats to the global pig industry [3–6]. Because no vaccine has been developed, a full understanding of the ecology and epidemiology of ASF is fundamental to implement effective control measures [2, 6, 7]. …”

Section: Introductionmentioning

confidence: 99%

Regional level risk factors associated with the occurrence of African swine fever in West and East Africa

et al. 2017

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BackgroundAfrican swine fever (ASF) causes severe socio-economic impacts due to high mortality and trade restrictions. Many risk factors of ASF have been identified at farm level. However, understanding the risk factors, especially wild suid hosts, determining ASF transmission at regional level remains limited.MethodsBased on ASF outbreak data in domestic pigs during 2006–2014, we here tested, separately for West and East Africa, which risk factors were linked to ASF presence at a regional level, using generalized linear mixed models.ResultsOur results show that ASF infections in the preceding year was an important predictor for ASF presence in both West and East Africa. Both pig density and human density were positively associated with ASF presence in West Africa. In East Africa, ASF outbreaks in domestic pigs were also correlated with higher percentages of areas occupied by giant forest hogs and by high-tick-risk areas.ConclusionsOur results suggest that regional ASF risk in East Africa and in West Africa were associated with different sets of risk factors. Regional ASF risk in West Africa mainly followed the domestic cycle, whereas the sylvatic cycle may influence regional ASF risk in East Africa. With these findings, we contribute to the better understanding of the risk factors of ASF occurrence at regional scales that may aid the implementation of effective control measures.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1953-z) contains supplementary material, which is available to authorized users.

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Review of the sylvatic cycle of African swine fever in sub-Saharan Africa and the Indian ocean

Cited by 132 publications

References 86 publications

Assessment of African Swine Fever Diagnostic Techniques as a Response to the Epidemic Outbreaks in Eastern European Union Countries: How To Improve Surveillance and Control Programs

Assessment of African Swine Fever Diagnostic Techniques as a Response to the Epidemic Outbreaks in Eastern European Union Countries: How To Improve Surveillance and Control Programs

Non-viraemic transmission of tick-borne viruses

Regional level risk factors associated with the occurrence of African swine fever in West and East Africa

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