Menangle virus

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Virology

Menangle virus (MenPV) is a member of the Rubulavirus genus of the subfamily Paramyxovirinae and family Paramyxoviridae (3). Paromyxoviruses are enveloped single stranded negative sense RNA viruses. The Rubulavirus genus contains over seven other species including the type species Mumps virus along with Human parainfluenza viruses 2 and 4, Mapuera virus, Porcine Rubulavirus, Simian virus 41 and Tioman virus (5, 11). Cloning and sequencing of menangle virus viral-specific DNA has confirmed that it is a distinct and new member of the Rubulavirus genus and there is no serological cross-reactivity with other Paramyxoviridae (3).

Epidemiology

In early 1997 a number of reproductive problems were observed in a commercial piggery in Menangle, New South Wales, Australia including a reduced farrowing rate and increases in still born and deformed piglets. The agent responsible was isolated in cell culture at the Elizabeth Macarthur Agricultural Institute also in Menangle, New South Wales from material from infected piglets (9). Two piggery workers were found to have had probable infection with the virus (4). Of over 250 potentially exposed workers tested serologically two were found to have high convalescent phase titres to menangle virus. Around the time of the isolation of menangle virus in pigs, both of these individuals had an influenza like illness and rash (4). Extensive serological surveys failed to find evidence of infection in pigs elsewhere in Australia and all other species in the vicinity examined were found to be seronegative including rodents, birds, cattle, sheep, cats and a dog (4, 7, 9). Menangle virus is closely related epidemiologically to the Henipaviruses Hendra and Nipah, also of the subfamily Paramyxovirinae. All three use fruit bats as their reservoir (1, 9). Menangle virus has subsequently been found to be more closely related antigenically to the Tioman virus (TioPV), another paramyxovirus, isolated from the urine of bats on Tioman Island, Malaysia in 2001 but not currently associated with any disease (5). Fruit bats are the only known reservoir host with no illness associated with serological evidence of infection. While the mode of transmission is not completely elucidated, feces and urine are considered likely sources (7). Control measures implemented as a result of the initial outbreak were successful with eradication of the virus from the pig population (7).

Clinical Manifestations

Human illness has been documented in only two piggery workers in New South Wales in 1997. Both had a febrile influenza like illness including lethargy, malaise, chills, headache and myalgia and a rash described as spotty or rubelliform. The illness was self-limiting and largely resolved within 10 to 14 days (4). This virus has been identified as a cause of reproductive disease (abortion, stillbirth, mummification and infertility) and congenital abnormalities of the brain, spinal cord and skeleton of pigs (8, 9, 10). No such manifestations have been found in humans.

Laboratory Diagnosis

Diagnosis of infection in humans and animals is made by detection of antibodies by virus neutralization or enzyme-linked immunoassay (6, 9). Serological testing has been conducted at the Australian Animal Health Laboratory, Geelong, Victoria, Australia and the Elizabeth Macarthur Agricultural Institute, Menangle, New South Wales, Australia. Histopathology and virus isolation in cell culture are also important diagnostic modalities (6, 9).

Pathogenesis

Menangle virus has been shown to cause viremia and infection of the uterus and fetus in pigs (7, 8). Experimental infection studies in 6 week old pigs have revealed a relatively short duration and low titre viremia with shedding of the virus in nasal and oral secretions, feces and urine for up to a week following a 2 to 3 day incubation period. Major sites of viral replication were identified as secondary lymphoid organs and intestine (2). There are no pathogenesis studies in humans.

SUSCEPTIBILITY IN VITRO AND IN VIVO

There are no in vitro or animal studies on drug susceptibility.

ANTIVIRAL THERAPY

There are no studies on the use of antiviral therapy for Menangle virus infection in animals or humans. Human infections so far have been mild and self-limiting.

ADJUNCTIVE THERAPY

No adjunctive therapies have been used.

ENDPOINTS FOR MONITORING THERAPY

No endpoints have been established.

VACCINES

No vaccines have been studied.

PREVENTION OR INFECTION CONTROL MEASURES

Since the route of transmission has not been confidently established the value of infection control measures is not entirely known. Standard precautions are recommended with particular attention to hand washing when handling blood and body fluids. In the original piggery outbreak temporary depopulation of individual units of the piggery with segregation of pigs based on age groups and attention to hygiene prevented further spread of infection (7). Given the likely bat reservoir it has been suggested that in endemic areas contact between bats and pigs should be minimized and pig farms should not be built in proximity to fruit bat colonies.

REFERENCES

1. Barr JA, Smith C, Marsh GA, Field H, Wang LF. Evidence of bat origin for Menangle virus, a zoonotic paramyxovirus first isolated from diseased pigs. Journal of General Virology. 2012;93(Pt 12):2590–4. [PubMed]

2. Bowden TR, Bingham J, Harper JA, Boyle DB. Menangle virus, a pteropid bat paramyxovirus infectious for pigs and humans, exhibits tropism for secondary lymphoid organs and intestinal epithelium in weaned pigs. Journal of General Virology. 2012;93(Pt 5):1007–16. [PubMed]

[PubMed]

3. Bowden TR, Westenberg M, Wang LF, Eaton BT, Boyle DB. Molecular characterization of Menangle virus, a novel paramyxovirus that infects pigs, fruit bats and humans. Virology 2001;283: 358-73. [PubMed]

4. Chant K, Chan R, Smith M, Dwyer DE, Kirkland P. Probable human infection with a newly described virus in the family Paramyxoviridiae. Emerging Infectious Diseases 1998;4:273-5. [PubMed]

5. Chua KB, Wang L-F, Lam SK, Crameri G, Yu M, Wise T, Boyle D, Hyatt AD, Eaton BT. Tioman Virus, a Novel Paramyxovirus Isolated from Fruit Bats in Malaysia. Virology. 2001;283:215–29. [PubMed]

6. Kirkland PD, and Davis RJ. Menangle Virus Infections. Australia and New Zealand Standard Diagnostic Procedures. Elizabeth Macarthur Agricultural Institute. 2006.

7. Kirkland PD, Love RJ, Philbey AW, Ross AD, Davis RJ, Hart KG. Epidemiology and control of Menangle virus infection in pigs. Australian Veterinary Journal 2001;79:199-206. [PubMed]

8. Love RJ, Philbey AW, Kirkland PD, Ross AD, Davis RJ, Morrissey C, Daniels PW. Reproductive disease and congenital malformations caused by Menangle virus in pigs. Australian Veterinary Journal 2001;79:192-8. [PubMed]

9. Philbey AW, Kirkland PD, Ross AD, Davis RJ, Gleeson AB, Love RJ, Daniels PW, Gould AR, Hyatt AD. An apparently new virus (family Paramyxoviridiae) infectious for pigs, humans and fruit bats. Emerging Infectious Diseases 1998;4:269-71. [PubMed]

10. Philbey A, Ross A, Kirkland P, Love R. Skeletal and neurological malformations in pigs congenitally infected with Menangle virus. Australian veterinary journal. 2007;85(4):134–40. [PubMed]

11. Virus Taxonomy: 2013 release. Available online: http://www.ictvonline.org/virusTaxonomy.asp (accessed on 13 June 2014).