Kanta Bhattacharjee

Genetic population structure of the malaria vector Anopheles baimaii in north-east India using mitochondrial DNA

BackgroundAnopheles baimaii is a primary vector of human malaria in the forest settings of Southeast Asia including the north-eastern region of India. Here, the genetic population structure and the basic population genetic parameters of An. baimaii in north-east India were estimated using DNA sequences of the mitochondrial cytochrome oxidase sub unit II (COII) gene.MethodsAnopheles baimaii were collected from 26 geo-referenced locations across the seven north-east Indian states and the COII gene was sequenced from 176 individuals across these sites. Fifty-seven COII sequences of An. baimaii from six locations in Bangladesh, Myanmar and Thailand from a previous study were added to this dataset. Altogether, 233 sequences were grouped into eight population groups, to facilitate analyses of genetic diversity, population structure and population history.ResultsA star-shaped median joining haplotype network, unimodal mismatch distribution and significantly negative neutrality tests indicated population expansion in An. baimaii with the start of expansion estimated to be ~0.243 million years before present (MYBP) in north-east India. The populations of An. baimaii from north-east India had the highest haplotype and nucleotide diversity with all other populations having a subset of this diversity, likely as the result of range expansion from north-east India. The north-east Indian populations were genetically distinct from those in Bangladesh, Myanmar and Thailand, indicating that mountains, such as the Arakan mountain range between north-east India and Myanmar, are a significant barrier to gene flow. Within north-east India, there was no genetic differentiation among populations with the exception of the Central 2 population in the Barail hills area that was significantly differentiated from other populations.ConclusionsThe high genetic distinctiveness of the Central 2 population in the Barail hills area of the north-east India should be confirmed and its epidemiological significance further investigated. The lack of genetic population structure in the other north-east Indian populations likely reflects large population sizes of An. baimaii that, historically, were able to disperse through continuous forest habitats in the north-east India. Additional markers and analytical approaches are required to determine if recent deforestation is now preventing ongoing gene flow. Until such information is acquired, An. baimaii in north-east India should be treated as a single unit for the implementation of vector control measures.

Emergence of oriental theileriosis in cattle and its transmission through Rhipicephalus (Boophilus) microplus in Assam, India

Aim: The aim of the present study was to investigate the presence of Theileria in blood samples of crossbred and indigenous adult cows raised under unorganized small scale farming system in a Babesia and Anaplasma endemic geographical area from Assam, India and to see its transmission through Rhipicephalus (Boophilus) microplus ticks. Materials and Methods: For the present study, 57 clinical cases of cattle suspected to be of hemoparasitic infections were taken into consideration. The parasites were identified based on morphology in giemsa stained blood smear followed by polymerase chain reaction (PCR). Sera samples were tested for T. annulata antibodies in plate and Dot-ELISA. PCR was also conducted in eggs of Rhipicephalus (Boophilus) microplus tick collected from a Theileria orientalis positive animal. Results: PCR amplified 1124, 776, and 160 bp DNA fragments of B. bigemina (64.91%), T. orientalis (21.05%) and A. marginale (14.03%), respectively. This assay further conducted in 12 T. orientalis positive blood samples with primers of Buffeli, Chitose, and Ikeda variants of T. orientalis showed 3 samples positive to Ikeda type and none for Buffeli and Chitose. Babesia bovis and Theileria annulata specific primers also did not amplify any fragment during the PCR assay of the blood samples. Further, all sera samples tested negative to T. annulata antibodies in Plate and Dot-ELISA. PCR conducted in eggs of R (B).microplus tick collected from a T. orientalis positive animal revealed presence of the parasite DNA. Gradual improvement in physical condition leading to complete recovery in 10 out of 12 T. orientalis infected clinical cases treated with buparvaquone(at 2.5mg/kg.b.wt I/M) was the feedback obtained from field veterinarians and the cattle owners. Conclusion: The present investigation represents the first report of occurrence of T. orientalis in cattle of Assam with involvement of pathogenic Ikeda strain in clinical outbreaks and its possible natural transmission by R (B). microplus through the transovarian mode.

Epidemiological aspects of Dirofilaria immitis infection in dogs from Assam of Northeast India

Abstract Objective To analyze the epidemiology of Dirofilaria immitis ( D. immitis ) infection in different categories of dogs in Assam. Methods Microscopy of blood in wet film preparation was conducted in two dog populations during 2009 and 2010, and data obtained were analyzed to investigate the infection pattern according to season, living condition, breed, sex and age of dogs. Results Examination of 424 clinically ill dogs (hospital population) presented at the referral Teaching Veterinary Clinical Complex, Guwahati, Assam revealed 5.42% cases microfilaraemic. Clinical cases of D. immitis infection were recorded throughout the year with 9.10% as the highest record during pre-monsoon and 1.12% as the lowest in the winter. Pet dogs staying indoor showed 4.76% microfilaria positive compared to 7.95% record among working dogs with restricted outdoor activity. Breed wise, Dalmatian dogs representing 3.53% of the study population were negative to microfilaria while among the positives, Doberman showed 30.76% infection rate as the highest and 2.94% lowest record in the Labrador. Rate of infection was slightly higher in the males (5.81%) than the females (4.81%). Dogs below 2 years of age were negative to microfilaria while it was 3.70% in 2–4 years age group with a rising trend reaching 28.00% as the highest in 6–8 years age group. Examination of non-descript (street dog population) adult dogs living outdoor showed 29.54% microfilaraemic, the rate of infection being higher in males (37.50%) than the females (25.00%). Similar non-descript dogs living indoor as pets however showed only 11.11% microfilaria positive. Conclusions The study shows endemicity of D. immitis in dogs of Assam with living condition and age as the host related important risk factors, which have significant role in its epidemiology.

Dirofilaria repens in dogs from Assam, India

Abstract Objective To access the prevalence of Dirofilaria repens (D. repens) in dogs from Assam, India. Methods A total of 223 blood samples from local dogs were examined with conventional (wet film and Knotts concentration technique), serological (ELISA test using Snap4Dx kits) and molecular techniques (targeting internal transcribed spacer-2 region using panfilarial primers) in Guwahati, Assam, India. Results The study revealed 4 (1.79%) cases of asymptomatic canine dirofilariasis caused by D. repens. The blood samples were positive for D. repens with microfilaremia on wet blood film, at Giemsa stained smear and under Knotts concentration technique, but were negative at Snap®4Dx test (IDEXX Laboratory, Westbrook, USA) which is specific for Dirofilaria immitis. D. repens could be detected by molecular test. Further confirmation was obtained on the basis of DNA sequencing and homology searching by basic local alignment search tool. Sequence analysis revealed that the species prevalent in Guwahati was genetically distinct from the other D. repens reported from elsewhere. Conclusions Occurrence of D. repens in dogs from this part of India was recorded for the first time, confirming the presence of a autochthonous canine reservoir for the zoonotic filarial nematode in Assam, India, where three cases of human subcutaneous and ocular infection with D. repens (dirofilariasis) have been reported.