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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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2011 - 20132
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Subject: Veterinary Parasitology × End date: 2014 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    STUDIES ON Dirofilaria immitis IN DOGS AND ITS ASSOCIATION WITH Wolbachia SPECIES
    (College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati-781022, 2013-06) Borthakur, Sonjoy Kumar; Deka, Dilip Kr.
    Dirofilaira immitis is an important canine filarial nematode. An epidemiological study was carried out to record the prevalence of D. immitis in dogs in two different geographical locations viz., Guwahati, Assam and Aizawl, Mizoram of North Eastern Region in India, from February, 2011 to July, 2012. The study also included to evaluate the persistence of Wolbachia endosymbiont with D. immitis. In the present study, dogs were grouped into three categories, i.e., stray, pet and working dogs, their respective numbers being 413, 266 and 103 irrespective of the study regions. Three different methods were used for the study, i.e., microscopy (wet film and KCT), immunological (Ag ELISA by SNAP®4Dx kit) and molecular techniques (PCR). The study revealed overall heartworm prevalence in Guwahati to be higher (18.23%) than in Aizawl (17.68%) irrespective of categories of dogs. Sex-wise, the infection was higher in male (18.12%) than in female (17.90%), though the difference was statistically non-significant. The overall efficacy percentage for detection of heartworm by wet film, KCT, Ag ELISA and PCR test revealed 6.26, 11.38, 18.03 and 13.93 percent, respectively. Ag ELISA test was found to be the best amongst the three types of tests compared. Using molecular tools, prevalence of D. immitis in dogs was 13.52 percent in Guwahati and in Aizawl was 14.62 percent. With PCR, 4 cases of D. repens could be diagnosed in stray dogs from Guwahati. The study revealed overall 22.69 percent occult infection, of which, highest cases were recorded in working dogs (60%). Occult infection was calculated by finding the difference between heartworm prevalence based on Ag ELISA and PCR test. Dot ELISA test using monoclonal antibody of D. immitis for detection of heartworm antigen in dog blood samples was standardized. The test revealed 72% specificity against known positive D. immitis blood samples at SNAP®4Dx commercial kit. Molecular technique using PCR was standardized to detect D. immitis using published primers with slight modification of thermal condition. Two different primers were used viz., specific primers for D. immitis only and another, pan filarial primers for detecting six different canine filariids. Both the primers resulted desired amplification product size against different filarial parasites. Molecular cloning and characterization of D. immitis for ITS-2 region of Guwahati isolates were conducted. The results showed the Guwahati isolates had a close relationship with that of South Asian isolates of D. immitis. Pair-wise homology analysis revealed 98.6 - 98.9% similarity with a few sequences available at NCBI GenBank. Similarly, phylogenetic analysis of D. repens encountered in Guwahati isolate was also done. Endosymbiont Wolbachia association with D. immitis worm as well as in heartworm infected blood was revalidated by PCR method. The findings were substantiated with the presence of the organisms in the worm’s lateral cord by fine structural studies conducted through transmission electron microscopy (TEM). Molecular evidence followed by sequence analysis of Wolbachia revealed 99.4 to 99.8% similarities with other sequences available in NCBI GenBank for Wolbachia endosymbiont of D. immitis. Finding of the present studies establish the endemicity of D. immitis in North East India and validates the association of Wolbachia endosymbiont in D. immitis. Record of D. repens warrants further detail studies owing to its zoonotic significance.
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    ThesisItemOpen Access
    STUDIES ON HAEMOPARASITIC INFECTIONS OF DOG WITH SPECIAL REFERENCE TO Dirofilaria immitis
    (Assam Agricultural University, Khanapara, Guwahati, 2011-08) Bhattacharjee, Kanta; Sarmah, P.C.
    The present research “Studies on haemoparasitic infections of dog with special reference to Dirofilaria immitis” was undertaken with a broad aim to assess by various methods the prevalence of haemoparasites in Assam of North East India, their clinical and clinicopathological significance and antigenic characterization of D. immitis. Microscopic study of Giemsa stained blood smears performed prospectively between January 2009 and December 2010 revealed a climate suited and highly enzootic situation with vector borne haemoparasites viz. Babesia gibsoni (47.16%), Ehrlichia platys (8.49%), Dirofilaria immitis (2.83%), Ehrlichia canis (2.12%), Babesia canis (1.41%), Hepatozoon canis (1.41%) and Ehrlichia ewingii (0.47%) in single or mixed infections. The prevalence was 57.31% in the hospital population comprising pet (58.03%) and working (54.54%) dogs and 63.64% in stray dog population in the prospective study against 23.19% record in the retrospective study. Clinical illness due to haemoparasites in the hospital dogs was recorded throughout the year. Variations in the infection rate due to age, breed and sex of dogs and seasons of the year were statistically non significant. Infection with Ehrlichia and Babesia were detected in dogs of all ages while in the case of D. immitis 80% positive cases were from 2-7 years age and 20% in the 8-10 years age group. Dogs below 2 years and above 10 years age were found microfilaria negative. Microscopic identity of Babesia species was confirmed in polymerase chain reaction (PCR), Indirect fluorescent antibody test (IFAT) using commercial B. canis IFA IgG antibody and B. gibsoni IFA IgG antibody Kits (Fuller Laboratories, USA) supplemented with conventional animal experimentation (sub-inoculation and splenectomy). PCR detection of B. canis and B. gibsoni in 16.36% and 3.63% respectively as single infection and 49.09% as mixed infection in tested samples was a significant finding which claimed 5.45% and 58.18% false negativity in B. gibsoni and B. canis detection respectively by microscopic method. In view of usual mixed infection found in PCR analysis detection of B. gibsoni in blood smear during field diagnosis could be considered as the biomarker of B. canis for the treatment purpose since the drug regimen against the two species are different. ELISA based commercial diagnostic kit, SNAP 3Dx (IDEXX, USA) confirming the microscopic identity of E. canis detected antibody in 32% dogs in a small group within the hospital population which was higher than the microscopic detection (2.12%). Among the hospital group the infection was found higher in working dogs than in the pet dogs. Seventy five percent E. canis seropositive dogs had E. platys inclusions as mixed infection suggesting the latter’s presence as biomarker for the former also. Haemoparasitic infection was confirmed in 57.31% cases through the assessment of parasite specific and non specific clinical symptoms. Regenerative anaemia characterized by biphagic erythrocyte sedimentation rate (ESR), appearance of nucleated erythrocyte, polychromasia, howell jolly body, thrombocytopenia with presence of giant platelets, variable leucogram usually with neutrophilia in blood smears were the prominent haematological findings in clinical babesiosis. In Ehrlichia, Hepatozoon and Dirofilaria infected clinical cases the anaemia was of non-regenerative type. Variable neutropenic leucopenia, thrombocytopenia with appearance of giant platelets, total absence or rare presence of howell jolly body, nucleated RBC and polychromasia in blood smear were the additional features specific to E. canis infection. However in mixed infection with Babesia and Ehrlichia features of regenerative anaemia were predominant. Biochemical evaluation showed wide variation leading to low albumin, elevated levels of total protein, globulin, creatinine and bilirubin. Dogs died of experimental and spontaneous babesiosis with nervine symptoms showed severe congestion, perivascular oedema with microabscess formation, neuronal degeneration in the brain tissue during histopathological examination. Enlarged heart with thickening of myocardium, right ventricular dilatation, thrombus formation in pulmonary artery and extensive areas of mild to moderate fatty changes were the pathological changes observed in heartworm positive carcasses. Antigenic analysis conducted in crude somatic male (SMA) and somatic female antigen (SFA) showed 9 and 17 clear protein bands in 12% SDS-PAGE of which 14, 20, 28 and 59 kDa protein fractions were common in both the antigens. Hyperimmune rabbit sera reacted with 3 protein bands in SMA and 5 protein bands present in SFA. Antibody ELISA performed in sera samples from hospital and stray dogs revealed 9.37% positivity at 1:50 dilution, 6.25% at 1:100 and 5.20% in 1:200 dilution. Necessity of a cost effective sensitive test to detect D. immitis during the amicrofilaraemic prepatent period was discussed.