We conducted cross-sectional and longitudinal studies to determine the distribution of and risk factors for seropositivity to Nipah virus (NiV) among Pteropus vampyrus and P. hypomelanus bats in Peninsular Malaysia. Neutralizing antibodies against NiV were detected at most locations surveyed. We observed a consistently higher NiV risk (odds ratio 3.9) and seroprevalence (32.8%) for P. vampyrus than P. hypomelanus (11.1%) bats. A 3-year longitudinal study of P. hypomelanus bats indicated nonseasonal temporal variation in seroprevalence, evidence for viral circulation within the study period, and an overall NiV seroprevalence of 9.8%. The seroprevalence fluctuated over the study duration between 1% and 20% and generally decreased during 2004–2006. Adult bats, particularly pregnant, with dependent pup and lactating bats, had a higher prevalence of NiV antibodies than juveniles. Antibodies in juveniles 6 months–2 years of age suggested viral circulation within the study period.

Emerging zoonoses threaten global health, yet the processes by which they emerge are complex and poorly understood. Nipah virus (NiV) is an important threat owing to its broad host and geographical range, high case fatality, potential for human-to-human transmission and lack of effective prevention or therapies. Here, we investigate the origin of the first identified outbreak of NiV encephalitis in Malaysia and Singapore. We analyse data on livestock production from the index site (a commercial pig farm in Malaysia) prior to and during the outbreak, on Malaysian agricultural production, and from surveys of NiV's wildlife reservoir (flying foxes). Our analyses suggest that repeated introduction of NiV from wildlife changed infection dynamics in pigs. Initial viral introduction produced an explosive epizootic that drove itself to extinction but primed the population for enzootic persistence upon reintroduction of the virus. The resultant within-farm persistence permitted regional spread and increased the number of human infections. This study refutes an earlier hypothesis that anomalous El Niño Southern Oscillation-related climatic conditions drove emergence and suggests that priming for persistence drove the emergence of a novel zoonotic pathogen. Thus, we provide empirical evidence for a causative mechanism previously proposed as a precursor to widespread infection with H5N1 avian influenza and other emerging pathogens.

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An outbreak of Nipah virus infection occurred in 1998 in Malaysia in which a total of more than 1 million pigs were culled and 109 people died from this disease. Samples were collected from frugivorous bats living in Malaysia that were considered to be a natural reservoir of Nipah virus. There were two kinds of fruit bats, the so-called flying fox and the small fruit bat. Samples were collected from small fruit bats and flying foxes caught by mist net traps. No antibody and no Nipah virus were detected from the samples of small fruit bat. However, an average 18% and 63% positive for antibody were detected from the samples of flying foxes living in the islands (Island flying fox) and peninsula of Malaysia (Malayan flying fox) respectively. Nipah virus was not isolated from either of the flying foxes. However, Nipah virus gene was detected from Malayan flying fox by real-time PCR. Reovirus like virus and other unknown viruses were isolated from Malayan flying foxes. From these results, flying fox was an important natural reservoir of Nipah virus and especially Malayan flying fox was considered to be more important as a natural reservoir.

This chapter reviews recent research on the emergence of the Nipah and Hendra viruses, two lethal zoonotic paramyxoviruses that first emerged from fruit bat reservoirs in Malaysia in 1999 and Australia in 1994, respectively. Large-scale environmental changes such as deforestation, intensification of agriculture, and encroachment of human populations into wildlife habitats may have driven changes in fruit bat migration patterns, feeding behavior, and the dynamics of viral transmission to promote the emergence of these pathogens. For example, fruiting trees planted next to hog containment facilities in Malaysia provide feeding and roosting sites for fruit bats that harbor the Nipah virus. These sites provide opportunities for pathogen spillover from bats to pigs, and ultimately to humans. The link between fruiting trees at hog farms and Nipah emergence has led to livestock management plans that specify buffer zones at pig farms where fruit trees are excluded.

To the Editor: Nipah virus (NiV) emerged in peninsular Malaysia in 1998 and 1999 as a respiratory and neurologic disease of domestic pigs and an acute febrile encephalitic disease in humans (1). Nipah virus infection is associated with a case-fatality ratio of 40% to 76% in humans (1,2). Cats (Felis catus) were infected with NiV at the site of the outbreak in northern Malaysia (3). Experimental studies have shown that cats are susceptible to Hendra virus and NiV (4,5). Infected cats shed NiV through the nasopharynx and in urine while viremic, and 1 (of 2) recovered from experimental NiV infection with a high neutralizing antibody titer (>256) within 21 days (5). Fruit bats of the genus Pteropus are believed to be the reservoir for NiV in Malaysia (6). In June 2000, NiV was isolated from partially eaten fruit and from the urine of Pteropus hypomelanus in the village of Air Batang on Tioman Island, Peninsular Malaysia (7). Although humans live in close proximity to these bats, no evidence for local human exposure to NiV has been seen (8). In contrast, epidemiologic evidence from recent NiV outbreaks in Bangladesh suggests that direct infection from pteropid bats may occur, possibly when bats are pregnant (2,9). Despite limited contact with bats, residents and visitors to Air Batang have ample opportunity for close contact with feral cats, which are often fed and sometimes housed by residents. Cats have been observed under trees that are occupied by roosting fruit bats in Air Batang. NiV could be transmitted from bats to cats through urine and then among cats oronasally, given their gregarious nature, which frequently includes mutual grooming. Cats are also frequently seen in close contact with humans in restaurants, on the tables, and in food preparation areas, where they are fed. If NiV is also present in bat fetal tissues, cats could become infected through contact with or by eating these tissues after mass births among bats. We tested feral cats from Air Batang for neutralizing antibodies to NiV to determine whether cats might play a role in the zoonotic transmission of Nipah virus. Fifty bats were captured from Air Batang and tested for NiV and neutralizing antibodies to NiV as part of a long-term NiV surveillance study (A. Rahman, unpub. data). Thirty-two cats were caught July 12–19, 2004, in a 200-m radius of a bat colony. Cats were anesthetized, and 3.0 mL blood was collected from the jugular vein or medial saphenous vein. Serum was allowed to separate at 4°C for 24 hours and was then further separated and frozen in liquid nitrogen. Serum was tested by serum neutralization test (SNT), which is considered the reference standard for serologic assays, at the Australian Animal Health Laboratory, Geelong, Australia, as described (5,10). The time of year was similar to the time when NiV was isolated from bats in 2000; however, none of the 32 cats (18 males, 14 females; 25 adults, 7 juveniles [ 32) to NiV on SNT, which suggests that virus had circulated in the colony since 2000. Our finding of no seropositive cats may be explained in 3 ways: 1) feral cats are rarely, if at all, exposed to NiV in nature; 2) the death rate from NiV infection in cats is so high that few or none survive with immunity; or 3) our sample size was too small to detect a seropositive cat. We believe that the first hypothesis is most likely. A low incidence of NiV infection in this population of bats (95% confidence interval for 0 of 50 bats, 0.00–0.71), combined with a short viremic period, would make transmission between bats and cats unlikely. However, if transmission occurred, we would expect to find some cats with a detectable titer (5). While the exact age of the cats in this survey was unknown, 25 (78%) of 32 were adults (>1 year of age) and may have been in Air Batang either in 2000, when NiV was isolated from bats, or during a more recent outbreak. We conclude that exposure of feral or peridomestic cats to Nipah virus on Tioman Island is rare and that the risk for zoonotic transmission is low.

The immunohistochemical reactivity of seven clones of mouse monoclonal antibodies raised to Nipah virus antigens were investigated using formalin-fixed, paraffin embedded porcine and equine lung tissues from experimental Nipah and Hendra virus infection, respectively. Either microwave irradiation or enzymatic digestion effectively unmasked the viral antigens in formalin-fixed, paraffin-embedded tissue sections. Four clones showed positive reaction to both Nipah virus-infected porcine lung tissue and Hendra virus-infected equine lung tissue. Two clones (11F6 and 13A5) reacted with Nipah virus-infected porcine lung tissue, but not with Hendra virus-infected equine lung tissue. These Nipah virus-specific monoclonal antibodies may therefore be useful for immunohistological diagnosis of Nipah virus infection and for further research on Nipah virus pathogenesis.

Eight clones of monoclonal antibodies (Mabs) to Nipah virus (NV) were produced against formalin-inactivated NV antigens. They reacted positive by indirect immunofluorescent antibody test, and one of them also demonstrated virus neutralizing activity. They were classified into six different types based on their biological properties. These Mabs will be useful for immunodiagnosis of NV infections in animals and further research studies involving the genomes and proteins of NV.

Chapter 3.14 Nipah Virus Diagnosis and Control in Swine Herds Peter W. Daniels, Peter W. DanielsSearch for more papers by this authorOng Bee Lee, Ong Bee LeeSearch for more papers by this authorAziz Jamaluddin, Aziz JamaluddinSearch for more papers by this author Peter W. Daniels, Peter W. DanielsSearch for more papers by this authorOng Bee Lee, Ong Bee LeeSearch for more papers by this authorAziz Jamaluddin, Aziz JamaluddinSearch for more papers by this author Antonio Morilla DVM, PhD, Dipl AE, Antonio Morilla DVM, PhD, Dipl AE Head of Swine Infectious Disease Branch, Centro, Nacional de Microbiología, Instituto Nacional de Investigaciones Forestales, Agrícolas y, Pecuarias (INIFAP), SAGARPA, MéxicoSearch for more papers by this authorKyoung-Jin Yoon DVM, PhD, Dipl ACVM, Kyoung-Jin Yoon DVM, PhD, Dipl ACVM Head of Virology and Molecular Microbiology, Section, Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State UniversitySearch for more papers by this authorJeffrey J. Zimmerman DVM, PhD, Dipl ACVPM, Jeffrey J. Zimmerman DVM, PhD, Dipl ACVPM Head of the Epidemiology and Applied Research Section, Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Iowa State UniversitySearch for more papers by this author Book Author(s):Antonio Morilla DVM, PhD, Dipl AE, Antonio Morilla DVM, PhD, Dipl AE Head of Swine Infectious Disease Branch, Centro, Nacional de Microbiología, Instituto Nacional de Investigaciones Forestales, Agrícolas y, Pecuarias (INIFAP), SAGARPA, MéxicoSearch for more papers by this authorKyoung-Jin Yoon DVM, PhD, Dipl ACVM, Kyoung-Jin Yoon DVM, PhD, Dipl ACVM Head of Virology and Molecular Microbiology, Section, Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State UniversitySearch for more papers by this authorJeffrey J. Zimmerman DVM, PhD, Dipl ACVPM, Jeffrey J. Zimmerman DVM, PhD, Dipl ACVPM Head of the Epidemiology and Applied Research Section, Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Iowa State UniversitySearch for more papers by this author First published: 01 January 2002 https://doi.org/10.1002/9780470376812.ch3nCitations: 1 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains section titled: Introduction Working Safely and Effectively During Nipah Virus Investigations The Diagnostic Approach On-Farm Laboratory Diagnostic Tests Histopathology, Electron Microscopy, and Immunohistochemistry Managing Pig Industries for Freedom from Nipah Virus Infection Conclusions References Citing Literature Trends in Emerging Viral Infections of Swine RelatedInformation

Nipah virus, family Paramyxoviridae, caused disease in pigs and humans in peninsular Malaysia in 1998-99. Because Nipah virus appears closely related to Hendra virus, wildlife surveillance focused primarily on pteropid bats (suborder Megachiroptera), a natural host of Hendra virus in Australia. We collected 324 bats from 14 species on peninsular Malaysia. Neutralizing antibodies to Nipah virus were demonstrated in five species, suggesting widespread infection in bat populations in peninsular Malaysia.