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camel pox

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camel pox

Summary

  • Last modified
  • 16 December 2021
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • camel pox
  • Overview
  • Camelpox is a contagious viral disease of camels that occurs throughout the camel-breeding countries of northern Africa, the Middle East, and Asia (Balamuru...

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Identity

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Preferred Scientific Name

  • camel pox

International Common Names

  • English: camel pox

Overview

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Camelpox is a contagious viral disease of camels that occurs throughout the camel-breeding countries of northern Africa, the Middle East, and Asia (Balamurugan et al., 2013). Camelpox virus (CMLV) naturally infects only the dromedary camel (Camelus dromedarius) and the Bactrian camel (Camelus bactrianus) (Wernery and Kaaden, 2002). Clinical manifestations of disease range from local and mild (pock lesions) to severe [mortality rate 10-28% in adults and 25-100% in young animals (Balamurugan et al., 2013)]. The disease occurs more frequently and more severely in young animals and pregnant females. A CMLV-based vaccine is available, but it is not widely used and only calves more than 6 months of age are protected (Duraffour et al., 2011).

Host Animals

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Animal nameContextLife stageSystem
Camelus bactrianus (Bactrian camel)Domesticated host
Camelus dromedarius (dromedary camel)Domesticated host
Lama guanicoeExperimental settings

Hosts/Species Affected

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CMLV is considered to solely naturally infect Old World camelids, which includes the dromedary camel (Camelus dromedarius) and the Bactrian camel (C. bactrianus). While experimental infection of guanacos (Lama guanicoe), a camelid native to South America, with CMLV has been successful (Wernery et al., 2000), natural infection of New World camelids has never been reported (Duraffour et al., 2011). Since 1972, there have been several attempts to infect animals others than camels with CMLV in order to define its host range. Horses, sheep, goat, cattle, rats, and guinea pigs all appeared to be refractory to CMLV infection (Duraffour et al., 2011). It is interesting to note, however, that a study in Saudi Arabia demonstrated that sheep and goats have prevalence rates of 6% and 10%, respectively, of anti-CMLV neutralizing antibodies (Housaw, 2007). These data might suggest the potential adaptation of CMLV to hosts other than camels in countries where the disease is enzootic; however, more research in this area needs to be done to support this hypothesis. Notably, two strains of CMLV have been shown to be pathogenic to rhesus monkeys. Strain etha-78 administered intradermally induced typical pox lesions (Falluji et al., 1979). Strain CM-G2 has also been shown to be pathogenic in monkeys, although no generalized rash was observed (Baxby, 1972).  In contrast, strain CP/Nw/92/2 did not induce any reaction when administered intradermally to monkeys; however, the dose of virus given was not stated (Khalafalla and Mohamed, 1998). Clearly, further experiments are required to clarify the pathogenicity of CMLV for nonhuman primates.

Vectors

The role for an arthropod vector in the transmission of camelpox has long been suspected. This idea is supported by the isolation of CMLV from Hyalomma dromedarii ticks during an outbreak of disease in the United Arab Emirates in 1995-1996 (Wernery et al., 1997a,b). H. dromedarii is the predominant tick species infesting camels. However, the question remains to be determined whether ticks are a true vector (or reservoir) of the virus or if they can only mechanically transmit the virus. Much work is need to determine what role, if any, ticks play in the epidemiology of camelpox.

Distribution

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Camelpox occurs in almost every region where camel breeding is practiced. Outbreaks of disease have been reported in many countries of the Middle East, Asia, Africa and southern Russia. These have included Iraq, Iran, Kazakhstan and Turkmenistan, India, United Arab Emirates, Saudi Arabia, Somalia, Ethiopia, Kenya, Sudan, Egypt, Niger, Mauritania, Morocco, and Syria (Wernery and Kaaden, 2002; Duraffour et al., 2011). Of note, camelpox has never been reported from Australia even though there are feral populations of dromedary camels and camel farming is practiced (Wernery and Kaaden, 2002). Similarly, disease has not been observed in llama and related species (New World camelids) of South America (Balamurugan et al., 2013).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 16 Dec 2021
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes

Africa

AlgeriaAbsentJul-Dec-2019
BeninAbsent, No presence record(s)Jan-Jun-2019
BotswanaAbsent, No presence record(s)Jul-Dec-2018
Cabo VerdeAbsent, No presence record(s)Jul-Dec-2019
Central African RepublicAbsent, No presence record(s)Jul-Dec-2019
Congo, Democratic Republic of theAbsent, No presence record(s)Jul-Dec-2019
Côte d'IvoireAbsent, No presence record(s)Jul-Dec-2019
DjiboutiAbsentJul-Dec-2019
EgyptAbsentJul-Dec-2019
EritreaAbsentJul-Dec-2019
EswatiniAbsent, No presence record(s)Jul-Dec-2019
EthiopiaPresentJul-Dec-2018
Guinea-BissauAbsent, No presence record(s)Jul-Dec-2019
KenyaAbsentJul-Dec-2019
LesothoAbsent, No presence record(s)Jan-Jun-2020
LiberiaAbsentJul-Dec-2018
LibyaAbsentJul-Dec-2019
MadagascarAbsent, No presence record(s)Jan-Jun-2019
MalawiAbsent, No presence record(s)Jul-Dec-2018
MauritaniaAbsentJul-Dec-2018
MauritiusAbsent, No presence record(s)Jul-Dec-2019
MayotteAbsent, No presence record(s)Jul-Dec-2019
MoroccoAbsentJul-Dec-2019
MozambiqueAbsent, No presence record(s)Jul-Dec-2019
NigerAbsentJul-Dec-2019
RéunionAbsent, No presence record(s)Jul-Dec-2019
RwandaAbsent, No presence record(s)Jul-Dec-2018
Saint HelenaAbsent, No presence record(s)Jan-Jun-2019
São Tomé and PríncipeAbsentJul-Dec-2019
SeychellesAbsent, No presence record(s)Jul-Dec-2018
Sierra LeoneAbsentJan-Jun-2018
SomaliaPresent, LocalizedJul-Dec-2020
South AfricaAbsent, No presence record(s)Jul-Dec-2019
South SudanAbsent, No presence record(s)Jan-Jun-2018
SudanAbsentJul-Dec-2019
TogoAbsent, No presence record(s)Jul-Dec-2019
TunisiaPresentJul-Dec-2019
UgandaAbsent, No presence record(s)Jul-Dec-2019
ZambiaAbsentJul-Dec-2018
ZimbabweAbsent, No presence record(s)Jul-Dec-2019

Asia

ArmeniaAbsent, No presence record(s)Jul-Dec-2019
AzerbaijanAbsentJul-Dec-2019
BahrainAbsentJul-Dec-2020
BangladeshAbsent, No presence record(s)Jan-Jun-2020
BhutanAbsent, No presence record(s)Jan-Jun-2020
BruneiAbsent, No presence record(s)Jul-Dec-2019
CambodiaAbsent, No presence record(s)Jul-Dec-2019
GeorgiaAbsent, No presence record(s)Jul-Dec-2019
IndonesiaAbsent, No presence record(s)Jul-Dec-2019
IranPresent, LocalizedJan-Jun-2019
IraqAbsentJul-Dec-2019
IsraelAbsentJul-Dec-2020
JordanAbsentJul-Dec-2018
KazakhstanPresentJan-Jun-2020
KuwaitAbsentJan-Jun-2019
KyrgyzstanAbsentJan-Jun-2019
LaosAbsent, No presence record(s)Jan-Jun-2019
LebanonAbsent, No presence record(s)Jul-Dec-2019
MalaysiaAbsent, No presence record(s)Jan-Jun-2019
MaldivesAbsent, No presence record(s)Jan-Jun-2019
MongoliaAbsent, No presence record(s)Jan-Jun-2019
MyanmarAbsent, No presence record(s)Jul-Dec-2019
NepalAbsent, No presence record(s)Jul-Dec-2019
PalestineAbsentJul-Dec-2019
PhilippinesAbsent, No presence record(s)Jul-Dec-2019
QatarAbsentJul-Dec-2019
Saudi ArabiaAbsentJan-Jun-2020
SingaporeAbsent, No presence record(s)Jul-Dec-2019
South KoreaAbsent, No presence record(s)Jul-Dec-2019
Sri LankaAbsentJul-Dec-2018
SyriaAbsentJul-Dec-2019
TaiwanAbsent, No presence record(s)Jul-Dec-2019
TajikistanAbsentJan-Jun-2019
TurkmenistanAbsentJan-Jun-2019
United Arab EmiratesAbsentJul-Dec-2020
UzbekistanAbsentJul-Dec-2019
VietnamAbsent, No presence record(s)Jul-Dec-2019
YemenAbsentJan-Jun-2020

Europe

AlbaniaAbsent, No presence record(s)Jul-Dec-2019
AndorraAbsent, No presence record(s)Jul-Dec-2019
AustriaAbsent, No presence record(s)Jul-Dec-2019
BelarusAbsent, No presence record(s)Jul-Dec-2019
BelgiumAbsent, No presence record(s)Jul-Dec-2019
Bosnia and HerzegovinaAbsent, No presence record(s)Jul-Dec-2019
BulgariaAbsent, No presence record(s)Jan-Jun-2019
CroatiaAbsent, No presence record(s)Jul-Dec-2019
CyprusAbsent, No presence record(s)Jul-Dec-2019
CzechiaAbsent, No presence record(s)Jul-Dec-2019
DenmarkAbsent, No presence record(s)Jan-Jun-2019
EstoniaAbsent, No presence record(s)Jul-Dec-2019
Faroe IslandsAbsent, No presence record(s)Jul-Dec-2018
FinlandAbsent, No presence record(s)Jul-Dec-2019
FranceAbsentJul-Dec-2019
GermanyAbsent, No presence record(s)Jul-Dec-2019
GreeceAbsent, No presence record(s)Jan-Jun-2018
HungaryAbsent, No presence record(s)Jul-Dec-2019
IcelandAbsent, No presence record(s)Jul-Dec-2019
IrelandAbsent, No presence record(s)Jul-Dec-2019
ItalyAbsent, No presence record(s)Jul-Dec-2020
LatviaAbsent, No presence record(s)Jul-Dec-2020
LiechtensteinAbsentJul-Dec-2019
LithuaniaAbsent, No presence record(s)Jul-Dec-2019
MaltaAbsent, No presence record(s)Jan-Jun-2019
MoldovaAbsent, No presence record(s)Jan-Jun-2020
MontenegroAbsent, No presence record(s)Jul-Dec-2019
NetherlandsAbsent, No presence record(s)Jul-Dec-2019
North MacedoniaAbsent, No presence record(s)Jul-Dec-2019
NorwayAbsent, No presence record(s)Jul-Dec-2019
PolandAbsent, No presence record(s)Jan-Jun-2019
PortugalAbsent, No presence record(s)Jul-Dec-2019
RomaniaAbsent, No presence record(s)Jul-Dec-2018
RussiaAbsent, No presence record(s)Jan-Jun-2020
San MarinoAbsent, No presence record(s)Jan-Jun-2019
SerbiaAbsent, No presence record(s)Jul-Dec-2019
SlovakiaAbsent, No presence record(s)Jul-Dec-2020
SloveniaAbsent, No presence record(s)Jul-Dec-2018
SpainAbsent, No presence record(s)Jul-Dec-2020
SwedenAbsent, No presence record(s)Jul-Dec-2020
SwitzerlandAbsent, No presence record(s)Jul-Dec-2020
UkraineAbsent, No presence record(s)Jul-Dec-2020
United KingdomAbsentJul-Dec-2019

North America

BahamasAbsent, No presence record(s)Jul-Dec-2018
BarbadosAbsent, No presence record(s)Jul-Dec-2020
BelizeAbsent, No presence record(s)Jul-Dec-2019
CanadaAbsent, No presence record(s)Jul-Dec-2019
Cayman IslandsAbsent, No presence record(s)Jan-Jun-2019
Costa RicaAbsent, No presence record(s)Jul-Dec-2019
CubaAbsent, No presence record(s)Jan-Jun-2019
CuraçaoAbsent, No presence record(s)Jan-Jun-2019
Dominican RepublicAbsent, No presence record(s)Jan-Jun-2019
El SalvadorAbsent, No presence record(s)Jul-Dec-2019
GreenlandAbsent, No presence record(s)Jul-Dec-2018
GuadeloupeAbsent, No presence record(s)Jul-Dec-2019
GuatemalaAbsent, No presence record(s)Jan-Jun-2019
HaitiAbsent, No presence record(s)Jul-Dec-2019
JamaicaAbsent, No presence record(s)Jul-Dec-2018
MartiniqueAbsent, No presence record(s)Jul-Dec-2019
MexicoAbsent, No presence record(s)Jul-Dec-2019
NicaraguaAbsent, No presence record(s)Jul-Dec-2019
PanamaAbsent, No presence record(s)Jan-Jun-2019
Saint LuciaAbsent, No presence record(s)Jul-Dec-2018
Saint Vincent and the GrenadinesAbsent, No presence record(s)Jan-Jun-2019
Trinidad and TobagoAbsent, No presence record(s)Jan-Jun-2018
United StatesAbsent, No presence record(s)Jul-Dec-2019

Oceania

AustraliaAbsent, No presence record(s)Jul-Dec-2019
Cook IslandsAbsent, No presence record(s)Jan-Jun-2019
Federated States of MicronesiaAbsent, No presence record(s)Jan-Jun-2019
FijiAbsentJan-Jun-2019
French PolynesiaAbsent, No presence record(s)Jan-Jun-2019
KiribatiAbsent, No presence record(s)Jan-Jun-2018
Marshall IslandsAbsent, No presence record(s)Jan-Jun-2019
New ZealandAbsent, No presence record(s)Jul-Dec-2019
PalauAbsent, No presence record(s)Jul-Dec-2020
Papua New GuineaAbsentJul-Dec-2018
SamoaAbsent, No presence record(s)Jan-Jun-2019
Timor-LesteAbsent, No presence record(s)Jul-Dec-2018
TongaAbsentJul-Dec-2019
VanuatuAbsent, No presence record(s)Jan-Jun-2019

South America

ArgentinaAbsent, No presence record(s)Jul-Dec-2019
BoliviaAbsent, No presence record(s)Jan-Jun-2019
BrazilAbsent, No presence record(s)Jul-Dec-2019
ChileAbsent, No presence record(s)Jan-Jun-2019
ColombiaAbsent, No presence record(s)Jul-Dec-2019
EcuadorAbsent, No presence record(s)Jul-Dec-2019
Falkland IslandsAbsent, No presence record(s)Jul-Dec-2019
French GuianaAbsent, No presence record(s)Jul-Dec-2019
GuyanaAbsent, No presence record(s)Jul-Dec-2018
ParaguayAbsent, No presence record(s)Jul-Dec-2019
PeruAbsent, No presence record(s)Jan-Jun-2019
SurinameAbsent, No presence record(s)Jan-Jun-2019
UruguayAbsent, No presence record(s)Jul-Dec-2019
VenezuelaAbsent, No presence record(s)Jan-Jun-2019

Pathology

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The CMLV usually enters through skin or via the oro-nasal route. After local replication and development of a primary skin lesion, the virus spreads to the local lymph nodes, which leads to a leukocyte-associated viraemia. Widespread secondary skin lesions appear a few days after the onset of viraemia and new lesions continue to appear for 2-3 days until viraemia subsides. The histopathology of skin lesions reveals characteristic cytoplasmic swelling, vacuolation and ballooning of the keratinocytes of the outer stratum spinosum of the epidermis. The rupture of these cells produces vesicles and localized oedema associated with perivascular cuffing of mononuclear cells, neutrophils and eosinophils. Marked epithelial hyperplasia may also occur at the borders of the skin lesions. The lung lesions are usually characterized by hydropic degeneration, proliferation of the bronchial epithelial cells associated with proliferative alveolitis and bronchiolitis infiltrated by macrophages, necrosis and fibrosis, which leads to obliteration of normal architecture (Balamurugan et al., 2013).

Diagnosis

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Camelpox can be diagnosed based on clinical signs; however, the disease can be confused with other viral diseases, such as contagious ecthyma (parapoxvirus) and papillomatosis (papillomavirus), or even non-infectious causes, such as insect bites. Thus, the use of laboratory-based diagnostic methods is recommended to differentiate camelpox from other infections. Tissues samples (skin lesions or organ biopsies) are the most useful specimens to identify the infectious agent. Several complementary laboratory-based methods can be used to specifically diagnose CMLV infection, including transmission electron microscopy (TEM), cell culture isolation, PCR, immunohistochemistry and demonstration of neutralizing antibodies. Exhaustive descriptions of the use of each of these procedures for camelpox diagnosis have been published elsewhere (Pfeffer et al., 1998b; Elliot and Tuppurainen, 2010).

TEM is a rapid and reliable method to demonstrate the presence of orthopoxvirus in scabs or tissue samples, although a relatively high concentration of virus is needed. While this technique enables the differentiation between virions of the orthopoxviruses (brick-shaped), parapoxviruses, (ovoid-shaped), and papillomavirus (round), the identity of the causative agent as CMLV must be confirmed using specific PCR or PCR plus sequencing (Elliot and Tuppurainen, 2010).

In addition to examination of scabs or tissue samples using TEM, virus isolation in cell culture should be performed in parallel. Blood, serum, and/or homogenized tissue samples can be used to infect cell cultures. As mentioned above, CMLV can grow on a wide variety of cell lines. However, Vero, MA-104, or Dubca cells, in which the virus grows easily, are generally preferred (Pfeffer et al., 1998b). Cultures should be monitored for the formation of cytopathic effects for 10-12 days.

For molecular assays, DNA can be extracted from various clinical materials (scabs, tissues biopsies, blood) or infected cell culture samples using a variety of commercial kits. Several PCR assays have been developed to identify CMLV, including those based on the detection of sequences encoding the A-type inclusion body (ATI), the hemagglutinin (HA), the Ankyrin repeat protein or the DNA polymerase (Duraffour et al., 2011). Many of these assays, however, require the additional steps of digesting the PCR amplicons with restriction enzymes and differentiation of the orthopoxvirus species based on the resulting amplicon fragment sizes. More recently, a PCR assay detecting sequences encoding for the Ankyrin repeat protein has been developed to specifically identify CMLV and to differentiate it from other orthopoxviruses (Balamurugan et al., 2009). Similarly, a multiplex PCR assay was recently developed to specifically detect CMLV, camel parapoxvirus, and camel papillomavirus, all of which are responsible for causing exanthematous skin conditions in camels (Khalafalla et al., 2015).

Given that all the orthopoxviruses cross-react with one another to some degree immunologically, immunodiagnostics have little utility, with the possible exception of the demonstration of neutralizing antibodies (Elliot and Tuppurainen, 2010). 

List of Symptoms/Signs

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SignLife StagesType
General Signs / Fever, pyrexia, hyperthermia Other|All Stages Sign
General Signs / Lymphadenopathy, swelling, mass or enlarged lymph nodes Other|All Stages Sign
Skin / Integumentary Signs / Skin papules Other|All Stages Sign
Skin / Integumentary Signs / Skin pustules Other|All Stages Sign
Skin / Integumentary Signs / Skin vesicles, bullae, blisters Other|All Stages Sign

Disease Course

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The disease is characterized by an incubation period of 9-13 days, followed by fever, enlarged lymph nodes, skin lesions, and prostration. Eruptions are mainly localized on the head, lips, nostrils, eyelids, and oral cavity. In general, the lesions heal in 4-6 weeks. However, in the more severe general form of the disease, lesions may spread over the body and even multiple lesions can be found on the mucous membranes of the mouth and respiratory and digestive tracts. Severely affected camels also develop proliferative poxviral lesions in the bronchi and lungs (Kinne et al., 1998). This form of the disease is often fatal (Pfeffer et al., 1998a). Additionally, pregnant animals may abort and mortality in affected animals can be exacerbated by septicaemia caused by secondary bacterial infections (Wernery and Kaaden, 2002).

Epidemiology

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Camelpox is a common highly contagious disease of Old World camelids (Camelus dromedarius and C. bactrianus); however, New World camelids are also susceptible. The disease occurs throughout the camel-breeding areas of Africa, the Middle East and Asia, including southern Russia and parts of the former Soviet Union. Infections are common among the camel herds of the nomadic pastoralists in the semi-desert zones of these countries. The disease has not been observed, however, in the introduced dromedary camel in Australia or the tylopoda (llama and related species) in South America (Balamurugan et al., 2013). A severe form of the disease is most often seen in young calves under the age of four years. These animals can experience a generalized form of disease with high morbidity (up to 92%) and mortality (up to 28%) rates (Jezek et al., 1983; Duraffour et al., 2011). In addition to young calves, pregnant females appear to be more susceptible to camelpox. Abortion rates can reach as high as 87%, as evidenced in Syria (Al-Zi'abi et al., 2007). The incidence and mortality rates are mostly higher in male, as opposed to female camels. In addition, various studies have demonstrated that the incidence and severity of outbreaks increased during the rainy season, while milder disease occurred during the dry season (Wernery et al., 1997a,b; Khalafalla and Ali, 2007). There are several hypotheses for these observations. It could be that CMLV strains of different virulence many explain the differences in pathogenicity seen between wet and dry seasons, although this has not been examined before (Duraffour et al., 2011). Another, perhaps more likely, possibility could be the involvement of arthropod vector populations that vary depending on the season (see hosts/vectors sections).

Impact: Economic

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According to the United Nations Food and Agriculture Organization, the total world camel population is approximately 23 million animals (http://faostat.fao.org). Camels are a major part of the economy in many countries.  They are used for nomadic pastoralism, transportation, racing, and production of milk, wool and meat (Wernery and Kaaden, 2002; Balamurugan et al., 2013). Thus, camelpox is a socio-economic concern as it incurs considerable loss in terms of morbidity, mortality, loss of weight and reduction in milk yield for the animal, in addition to economic losses to the camel racing and transportation industries.

Zoonoses and Food Safety

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During the time of the smallpox eradication campaign, the question arose as to whether camels could serve as an animal reservoir for variola virus and whether camelpox virus could be transmitted to humans. Various observations suggested that human infections with camelpox virus were rare. Based in part on these observations, Baxby concluded that camelpox virus was significantly different from variola virus and incapable of infecting man (Baxby, 1972). However, rare human cases of camelpox have been reported. It was reported that people drinking milk from camelpox-affected animals developed ulcers on the lips and in the mouth; however, these reports were unable to be confirmed  (Davies et al., 1975). Additional studies sought to assess the risk of camelpox virus infections in humans. Of 465 camel herdsmen handling affected camels, only one camel handler, who was not vaccinated against smallpox, developed pock-like lesions on his arm and seroconverted for orthopoxvirus, but again, the exact cause of the infection was not determined by specific diagnostic tests (Jezek et al., 1983).

The first conclusive evidence of zoonotic camelpox virus infection in humans occurred during an outbreak of disease in camels in India during 2009. During this outbreak, three human cases (who were camel handlers) were reported having clinical manifestations of camelpox, including papules, vesicles, ulceration, and ultimately scabs over their fingers and hands (Bera et al., 2011). Serum samples of the three suspected cases showed neutralizing antibodies against camelpox virus. Furthermore, in one of the three cases, viral DNA could be detected by PCR specific for camelpox virus genes (Bera et al., 2011). Nevertheless, the paucity of human cases reported in the more than 45 years since the virus was first isolated suggests that zoonotic human camelpox is very rare.

Disease Treatment

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Given the increased concerns over the past decade that orthopoxviruses, including smallpox and monkeypox viruses, could be used as biological weapons, there has been increased efforts in the development of antivirals active against poxviruses (Prichard and Kern, 2012). Many of these could be envisaged for the treatment of camelpox. In particular, three of the most active anti-poxvirus drugs include cidofovir (Vistide; Gilead, CA, USA), its lipid derivative brincidofovir (CMX001; Chimerix Inc., NC, USA), and ST-246 (SIGA Inc., OR, USA) (Duraffour et al., 2011). Cidofovir and brincidofovir are active against a broad range of DNA viruses, including poxviruses, and both compounds target the viral DNA polymerase. Cidofovir is already marketed for the treatment of cytomegalovirus retinitis in HIV-infected humans. It is not orally bioavailable and thus must be given by intravenous injection. In addition, cidofovir is nephrotoxic in humans. As a consequence, a lipid derivative of cidofovir, brincidofovir or CMX001, was developed that has been shown to be orally bioavailable and did not show any toxicity in mice (Ciesla et al., 2003) or in humans undergoing a Phase I clinical study (http://www.chimerix.com/). It was previously reported that in cell culture, cidofovir inhibited 50% of CMLV replication (Smee et al., 2002; Duraffour et al., 2007a). The antiviral activity of brincidofovir against CMLV has not been reported. In contrast, ST-246 is a unique compound that blocks a late step in virus assembly by preventing intracellular virus formation and subsequent virus egress from the cell (Jordan et al., 2010). ST-246 is a potent inhibitor that is specific to orthopoxviruses. It is oral bioavailable, and has been shown to have a good safety profile in both humans and monkeys. In the case of CMLV, the activity of ST-246 has only been evaluated in vitro; however, the antiviral activity was very potent (EC50 value of 0.01 µM in Vero cells) (Duraffour et al., 2007b). While potent inhibitors of CMLV and other orthopoxviruses, none of these drugs have been evaluated for use in the treatment of camelpox in camels

Prevention and Control

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Over the years, outbreaks of camelpox have resulted in major economic losses in several Middle Eastern countries (Duraffour et al., 2011). As a result, much research has focused on the development of prophylactic vaccines to contain the spread of camelpox. To date four camelpox vaccines have been developed and evaluated. They are all made from the CMLV and include the Jouf-78 strain (Hafez et al., 1992), VD47/25 strain (Nguyen et al., 1996), Ducapox 298/89 (Wernery and Zachariah, 1999), and the CMLV-T8 strain (El Harrak and Loutfi, 2000). The Jouf-78 strain is an attenuated CMLV strain that has been passaged 80 times in cell culture and has been shown to offer full protection from CMLV challenge. Based on field studies, a single dose of vaccine ranging from 103 to 104 TCID50 provides full protection.  The attenuated strain VD47/25, also passaged 80 times in cell culture, was evaluated in experiments in Mauritania. This strain was found to be innocuous in camels at a dose of 104.7 TCID50 given subcutaneously and fully protected camels from an otherwise lethal CMLV infection (Nguyen et al., 1996). In the United Arab Emirates, a modified live CMLV vaccine obtained from passaging the strain CaPV298-2 in Vero cells was used. The vaccine named Ducapox for “DUbai CAmelPOX” vaccine is produced by Highveld Biological of South Africa. It was used for field vaccination just before the onset of a large camelpox outbreak in Dubai in 1993-1994. Among 2000 vaccinated camels, seven developed disease, but it was not known if these animals were infected before vaccination or if they were true vaccination failures (Pfeffer et al., 1996). Furthermore, in was shown in two animals that protection lasted for 6 years (Wernery and Zachariah, 1999). Vaccine efficacy was also demonstrated in new world camelids against an otherwise lethal CMLV challenge (Wernery et al., 2000). In Morocco, a vaccine containing an inactivated CMLV (strain T8), combined with an adjuvant, is manufactured and distributed by Biopharma (El Harrak and Loutfi, 2000). The T8 strain was isolated from scabs during an outbreak in Morocco in 1984. The vaccine has been shown to be safe in young and adult camels and elicits neutralizing antibodies (El Harrak and Loutfi, 2000). However, it requires a second injection after one month for efficient protection.

Due to the immaturity of the immune system, it is generally recommended to give any vaccine to camels that are at least 6 months old, and a second vaccination might be necessary for young calves (Duraffour et al., 2011). Antivirals could play a role in preventing the spread of the disease in animals that are younger than 6 months old.

References

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Afonso CL, Tulman ER, Lu Z, Zsak L, Sandybaev NT, Kerembekova UZ, Zaitsev VL, Kutish GF, Rock DL, 2002. The genome of camelpox virus. Virology, 295(1):1-9

Al-Zi'abi O, Nishikawa H, Meyer H, 2007. The first outbreak of camelpox in Syria. Journal of Veterinary Medical Science, 69(5):541-543. http://www.soc.nii.ac.jp/jsvs

Azwai SM, Carter SD, Woldehiwet Z, Wernery U, 1996. Serology of Orthopoxvirus cameli infection in dromedary camels: analysis by ELISA and Western blotting. Comparative Immunology, Microbiology and Infectious Diseases, 19(1):65-78

Baxby D, 1972. Smallpox-like viruses from camels in Iran. Lancet, 2(No.7786):1063-1065

Bera BC, Shanmugasundaram K, Sanjay Barua, Venkatesan G, Nitin Virmani, Riyesh T, Gulati BR, Bhanuprakash V, Vaid RK, Kakker NK, Malik P, Manish Bansal, Gadvi S, Singh RV, Yadav V, Sardarilal, Nagarajan G, Balamurugan V, Hosamani M, Pathak KML, Singha RK, 2011. Zoonotic cases of camelpox infection in India. Veterinary Microbiology, 152(1/2):29-38. http://www.sciencedirect.com/science/journal/03781135

Bray M, Babiuk S, 2011. Camelpox: target for eradication? Antiviral Research, 92(2):164-166

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Distribution References

OIE, 2018. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int/

OIE, 2018a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int

OIE, 2019. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int/

OIE, 2019a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int/

OIE, 2020. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int/

OIE, 2020a. World Animal Health Information System (WAHIS). Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated. https://wahis.oie.int/

Links to Websites

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CFSPH: Animal Disease Informationhttp://www.cfsph.iastate.edu/DiseaseInfo/index.php"Animal Disease Information" provides links to various information sources, including fact sheets and images, on over 150 animal diseases of international significance.
OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animalshttp://www.oie.int/en/international-standard-setting/terrestrial-manual/access-online/The Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Terrestrial Manual) aims to facilitate international trade in animals and animal products and to contribute to the improvement of animal health services world-wide. The principal target readership is laboratories carrying out veterinary diagnostic tests and surveillance, plus vaccine manufacturers and regulatory authorities in Member Countries. The objective is to provide internationally agreed diagnostic laboratory methods and requirements for the production and control of vaccines and other biological products.

Contributors

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06/04/17 Original text by:

Chris A. Whitehouse, 1425 Porter Street, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA

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