Pergamon Comp. Immun. Microbid. infecf. Dis. Vol. 18, No. I, pp. 73-74, 1995

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SHORT COMMUNICATION

A NOTE ON THE CONCURRENT ISOLATION, FROM HORSES AND PONIES, OF INFLUENZA

A/EQ-1 AND A/EQ-2 VIRUSES FROM AN EPIDEMIC OF EQUINE INFLUENZA IN INDIA

GURKIRPAL SINGH* Department of Veterinary Public Health and Epidemiology, Punjab Agricultural University,

Ludhiana-141004. India

(Received for publication 26 April 1994)

Abstract-A/eq-1 and A/eq-2 influenza viruses were isolated simultaneously from an epidemic of equine influenza in north India. Evidently, both types of equine influenza viruses circulated in the equine population at the same time.

R&me--On a is016 simultanbment les virus influenza A/eq-1 et A/eq-2 lors d’une bpidemie d’influenza 6quine en Inde du Nord. De faGon evidente, les deux types de virus influenza circulaient en m&me temps dans la population des Cquidis.

An epidemic of equine influenza which began in and around Delhi in January 1987, spread to distant areas in northern and central India. The outbreak of illness was seen in Union Territory of Chandigarh at the tail end of February and early part of March and in different places in the state of Punjab and other adjoining areas in later part of March and April 1987.

Altogether 28 nasal swab specimens from clinically sick horses and ponies were collected and inoculated into 10 to 1 l-day old embryonated eggs. Four haemagglutinating viral agents were isolated.

The isolates were tested in haemagglutination inhibition (HI) tests using the procedure of W.H.O. [l]. The hyperimmune rabbit sera against prototype A/eq-2 viruses (A/eq/Miami/l/63, A/eq/Sachyama/ l/7 1 and A/eq/Fontainebleau/1/79) and A/eq/Prague/l/56 virus were used.

Two viral isolates, Ludhiana/3/87 and Ludhiana/8/87 were found to contain antigens inhibited by Miami/63 antiserum [2], Sachyama/7 1 and Font./79 antiserum, thus identify- ing the agents as A/eq-2 viruses. In neuraminidase inhibition tests, Ludhiana/8/87 isolate was found similar to the prototype Miami/63 and Font./79 (H3N8) used. The third viral isolate, Ludhiana/6/87, which showed variable reaction appeared to be a possible mixture and is still under study.

*Present address: Department of Veterinary Bacteriology and Virology, Punjab Agricultural University, Ludhiana-141004, India.

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74 Short Communication

The isolate, Ludhiana/5/87, was inhibited by Prague/56 antiserum. This result together with neuraminidase analysis to be reported elsewhere indicate that the isolate was antigenically similar to the prototype Prague/56 virus and was therefore identified to be H7N7 subtype. The isolation of A/eq-1 is interesting since the serotype has not been reported from anywhere in the world since 1980 and in view of the increasing A/eq-2 virus activities in the world especially in Asia, in the recent past.

The concurrent isolation of A/eq-1 and A/eq-2 viruses in this study and the demon- stration of A/eq-I and A/eq-2 HI antibodies in horse sera collected postepidemic [3] indicate that during the equine influenza epidemic in 1987, both types of equine influenza viruses were active in North India. It appeared to be the first instance of confirmed existence of both types of equine influenza virus in the same epidemic.

Acknowledgemmt-The author is grateful to Dr J. J. Skehel, World Influenza Centre, National Institute for Medical Research, London for confirmation of local isolates as A/eq-I & A/eq-2 and for his helpful advice.

REFERENCES

I. W.H.O. Concepts and Procedures for Laboratory Based Influenza Surveillance, U.S. Department of Health and Human Services/Public Health Services/Centres for Disease Control, I21 I, Geneva 27, Switzerland (1982).

2. Singh G., Oberoi M. S., Kwatra M. S. and Gill S. S. Isolation of influenza virus from horses in equine influenza outbreak of 1987. Current Sri. 56, 128551286 (1987).

3. Singh G. Equine influenza 1987, post-epidemic serological study in North India. J. Eq. Vet. Sci. 12, 3422344 (1992).