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Nipah Virus and Lychees

Dr Swati Tomar

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The natural reservoir for Nipah virus is still under investigation, but preliminary data suggest that bats of the genus Pteropus are also the reservoirs for Nipah virus in Malaysia.

Transmission electron micrographs showing some of the ultrastructural morphology found in the Nipah virus. The figure at the top depicts a negative stain electron microscopic image of a single long stranded nucleocapsid, on the bottom left depicts a thin section EM image of a mature virus particle, and on the bottom right depicts a thin section EM image of nucleocapsids apposed to the plasma membrane of an infected cell.
CDC/Cynthia Goldsmith

Immunohistochemistry of a tissue section showing cytoarchitectural histopathologic changes associated with a Nipah virus infection.
CDC/Dr Brian Mahy

Immunohistochemistry of a canine renal specimen showing cytoarchitectural histopathologic changes associated with a Nipah virus infection. CDC/Dr Brian Mahy

A seemingly innocuous summer fruit, Lychee (Litchi chinensis Sonn., Sapindaceae), made headlines across Indian newspapers as being the primary cause of deaths of seven children in Malda district of West Bengal. Most probable reasons were found to be a rare form of viral encephalopathy which results in high grade fever, vomiting and convulsions.

This outbreak was first reported in China and Vietnam (J Paireau, 2012) with a recent report from Muzaffarpur, Bihar (K Laserson, 2013). The viral infection referred to as acute encephalitis syndrome (AES) or acute neurological syndrome (ANS) was locally termed Ac Mong encephalitis (AME) in Vietnam, after the Vietnamese word for nightmare. The Vietnamese study reported that the epidemics occurred earlier in the districts that harvested litchis during May–June than in those that harvested litchis during June–July (J Paireau, 2012). One possible explanation for transmission of virus from a fruit to humans was that fruit-bearing litchi trees attracted bats, which in turn might be the reservoir for the putative pathogen. Mosquitoes could thus be a carrier for the virus from the infected bats to humans (J Paireau, 2012). Other possibilities could be direct contamination of litchis with bat saliva, urine, or guano (Wacharapluesadee S, 2005) or drawing parallels from Chandipura virus, transmission could be from insects found in litchi trees or phlebotomine sand flies (Geevarghese G, 2005). Lastly, there might be a connecting link between human feces used as fertilizers to enhance litchi growth and contamination of soil with enteroviruses, which are notorious for causing fatal encephalitis in malnourished children (Sapkal GN, 2009). The leading litchi-producing countries happen to be China, India, Taiwan, Thailand, and Vietnam (Evans EA, 2005) and that might be the reason why these countries are experiencing such outbreaks.

Amidst these possibilities, the actual causative pathogen and its transmission is still unknown. An epidemiological study delineating the causal factors of ANS caused by Litchi in India would bring more insights into the issue.

Additionally, Lychee seed extracts were found to possess significant in-vitro antiviral properties against Coxsackie virus B3 (CVB3) Nancy strain and herpes simplex virus 1 (HSV-1) (Xinya Xu, 2010). Oligonol, a purified phenolic extract from lychee fruit and green tea, was reported to serve as antiviral agent against betanodavirus (Ichinose T, 2013) and influenza virus A/HK (H3N2) (L. Gangehei, 2010).

What is intriguing is that despite possessing such inherent antiviral properties, litchi happens to be a carrier for viral encephalopathy! It would be of interest to study the brain extracts of patients for viral pathogens and do a functional analysis of antiviral properties against the specific virus types.


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This page last changed on Wednesday, November 23, 2016
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