Prevalence of antibodies to Leptospira serovars in rodents and shrews trapped in low and high endemic areas in Thailand.
OBJECTIVE
To investigate the prevalence of antibodies to Leptospira serovars in rodents and shrews trapped in urban and rural areas in low and high endemic areas in Thailand.


METHODS
A total of 1,664 serum samples were collected from rodents and shrews in areas of low and high endemicity for leptospirosis. Four areas classified by case rates (CR) per 100,000 population of leptospirosis were urban Area I Bangkok (CR = 0.07), rural Area II (CR = 0.24), rural Area III (CR = 1.97) and rural Area IV (CR = 48.20). All serum samples were investigated for antibodies to leptospires by microscopic agglutination test (MAT) using antigens from each of the 22 pathogenic serovars of Leptospira interrrogans: australis, autumnalis, ballum, bangkok, bataviae, bratislava, canicola, celledoni, copenhageni, djasiman, grippotyphosa, hardjo, hebdomadis, icterohaemorrhagiae, javanica, pomona, pyrogenes, rachmati, saigon, sejroe, tarassovi and wolffi and one non-pathogenic strain of L. biflexa serovar patoc.


RESULTS
Ninety-four (5.6%) serum samples were positive for Leptospira antibodies. The most commonly detected antibodies were to serovars pyrogenes (39.1%), sejroe (19.1%), bataviae (10.0%), pomona (6.4%), autumnalis (5.5%), copenhageni (3.6%) and javanica (3.6%). The positive rates in Area I, II, III and IV were 7.6 per cent, 2.9 per cent, 4.6 per cent and 7.1 per cent, respectively. The seroprevalence in rural areas tended to increase significantly with high endemicity for leptospirosis (Chi-square for trend, p = 0.04). The seropositive rates by animal species were 39/496 (7.9%), 22/322 (6.8%), 23/492 (4.7%), 6/170 (3.5%), 4/175 (2.3%), 0/4 (0%) and 0/5 (0%) in Rattus norvegicus, Rattus exulans, Rattus rattus, Bandicota indica, Bandicota savilei, Mus musculus and Suncus murinus, respectively. There was a statistical trend between seropositive rates in R. exulans and endemicity for leptospirosis (Chi-square for trend, p = 0.04).


CONCLUSIONS
The 5.6 per cent of rodents and shrews trapped in urban and rural areas in Thailand were reservoirs of leptospires. The results of high seroprevalence in rats also indicate the high endemicity for leptospirosis.
Kositanont
Uraiwan
U
Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
Naigowit
Pimjai
P
Imvithaya
Amporn
A
Singchai
Chantra
C
Puthavathana
Pilaipan
P
D000372:Agglutination Tests; D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis*; D016009:Chi-Square Distribution; D019353:Endemic Diseases / Q000706:statistics & numerical data*; D007919:Leptospira / Q000145:classification* / Q000276:immunology*; D007922:Leptospirosis / Q000453:epidemiology*; D015995:Prevalence; D011336:Probability; D051381:Rats; D012307:Risk Factors; D012376:Rodent Diseases / Q000453:epidemiology*; D012377:Rodentia; D012424:Rural Population; D016036:Seroepidemiologic Studies; D012788:Shrews; D013785:Thailand / Q000453:epidemiology; D014505:Urban Population
D000907:Antibodies, Bacterial