Twelve years of rabies surveillance in Sri Lanka, 1999-2010.

BACKGROUND: Rabies is endemic in Sri Lanka, but little is known about the temporal and spatial trends of rabies in this country. Knowing these trends may provide insight into past control efforts and serve as the basis for future control measures. In this study, we analyzed distribution of rabies in humans and animals over a period of 12 years in Sri Lanka. METHODS: Accumulated data from 1999 through 2010 compiled by the Department of Rabies Diagnosis and Research, Medical Research Institute (MRI), Colombo, were used in this study. RESULTS: The yearly mean percentage of rabies-positive sample was 62.4% (47.6-75.9%). Three-fourths of the rabies-positive samples were from the Colombo, Gampaha, and Kalutara districts in Western province, followed by Galle in Southern province. A high percentage of the rabies samples were from dogs (85.2%), followed by cats (7.9%), humans (3.8%), wild animals (2.0%), and livestock (1.1%). Among wild animals, mongooses were the main victims followed by civets. The number of suspect human rabies cases decreased gradually in Sri Lanka, although the number of human samples submitted for laboratory confirmation increased. CONCLUSIONS: The number of rabid dogs has remained relatively unchanged, but the number of suspect human rabies is decreasing gradually in Sri Lanka. These findings indicate successful use of postexposure prophylaxis (PEP) by animal bite victims and increased rabies awareness. PEP is free of charge and is supplied through government hospitals by the Ministry of Health, Sri Lanka. Our survey shows that most positive samples were received from Western and Southern provinces, possibly because of the ease of transporting samples to the laboratory. Submissions of wild animal and livestock samples should be increased by creating more awareness among the public. Better rabies surveillance will require introduction of molecular methods for detection and the establishment of more regional rabies diagnostic laboratories.

Molecular epidemiology of human rabies viruses in Sri Lanka.

Rabies is a lethal zoonotic disease caused by the rabies virus, which is transmitted by rabid animals to humans. Rabies is prevalent in all continents, with over 60% of human deaths occurring in Asia. Sri Lanka is a rabies-endemic country. This study shows that rabies afflicted more older individuals than children in Sri Lanka between 2008 and 2010. This novel finding indicates that older people in Sri Lanka should be more aware of the risk of rabies. Phylogenetic analyses of the rabies N and G genes showed that the Sri Lankan rabies viruses are distinct and probably originated from a single clone. The G-L noncoding region is highly diverse, and is suitable for the analysis of virus evolution within a country. A phylogenetic analysis of this region showed high diversity in the currently circulating Sri Lankan rabies viruses, which can be divided into seven clades. Some clades are unique to a specific geographic region, whereas others occur at multiple locations. This indicates that the movement of dogs, the main rabies-transmitting animal in Sri Lanka, is restricted in some areas but less limited in others. These data may help to formulate a more efficient rabies control program in Sri Lanka.

Evaluation of a monoclonal antibody-based rapid immunochromatographic test for direct detection of rabies virus in the brain of humans and animals.

Rabies diagnosis uses a direct fluorescent antibody test (FAT) that is difficult, costly, and time-consuming, and requires trained personnel. We developed a rapid immunochromatographic test (RICT) for the diagnosis of rabies. The efficacy of the RICT was compared with that of the FAT. Brain samples were collected from humans, dogs, cats, and other animals in Sri Lanka (n = 248), Bhutan (n = 27), and Thailand (n = 228). The sensitivity (0.74-0.95), specificity (0.98-1.0), positive predictive value (0.98-1.0), negative predictive value (0.75-0.97), accuracy (0.91-0.98), and kappa measure of agreement (0.79-0.93) were all satisfactory for animal samples and samples preserved in 50% glycerol saline solution. Because the RICT showed high sensitivity but low specificity with human brain samples, it is unsuitable for confirming rabies in humans. No amino acid substitutions were found in the antibody attachment sites of the nucleoprotein gene with FAT-positive, RICT-negative samples. The RICT is reliable, user friendly, rapid, robust, and can be used in laboratories with a modest infrastructure.

Novel sylvatic rabies virus variant in endangered golden palm civet, Sri Lanka.

Information is scarce about sylvatic rabies virus in Asia and about rabies in palm civets. We report a novel sylvatic rabies virus variant detected in a golden palm civet in Sri Lanka. Evolutionary analysis suggests the virus diverged from canine rabies viruses in Sri Lanka in ≈1933 (range 1886-1963).

Whole-genome analysis of a human rabies virus from Sri Lanka.

The complete genome sequence of a human rabies virus, strain H-08-1320, from Sri Lanka was determined and compared with other rabies viruses. The size of the genome was 11,926 nt, and it was composed of a 58-nucleotide 3' leader, five protein genes--N (1353 nt), P (894 nt), M (609 nt), G (1575 nt), and L (6387 nt)--and a 70-nt 5' trailer. The intergenic region G-L contained 515 nt. The sizes of the nucleoprotein, phosphoprotein, matrix-protein, glycoprotein and large-protein was 450, 296, 202, 524 and 2,128 residues, respectively. The phosphoprotein and large protein were one amino acid shorter and longer, respectively, than those of most rabies viruses. The glycoprotein of H-08-1320 had a unique amino acid substitution at antigenic site I. Whole-genome phylogenetic analysis showed that strain H-08-1320 formed an independent lineage and did not cluster with rabies viruses from other countries.