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CHARACTERIZATION AND COMPARATIVE SUSCEPTIBILITY OF HIGHLY PATHOGENIC AVIAN INFLUENZA H5N1 VIRUS INFECTIONS IN CHICKENS AND DUCKS
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Page will reload when a filter is selected or excluded.- Amoebiasis exemplifies a disease of protean manifestations which presents many perplexing problems. In this thesis an attempt is made to define a number of the wide variations which have been observed in the pathological manifestations of the disease. The work consists of both retrospective and prospective Studies. The retrospective study involved a review of the 7922 protocols of the autopsies at the University College Hospital, Ibadan, during the ten year period 1958 to 1967. 135 cases in which lesions of amoebiasis were described, were selected for special study using 276 cases of other diarrhoeal diseases as controls. The results of this review defined the pathology and complications of amoebiasis seen at the UCH, during the period covered by this study. A prospective study which included field surveys. laboratory studies on patients and controls; and in-vitro studies of the parasite was also carried out. Parasitological, biochemical and immunological techniques were applied in the prospective study of 1291 subjects in a field survey. In addition some 200 hospital materials were included in the prospective study. The results obtained provided the basis for the suggestions made concerning the different methods that can be applied to the future study of the prevalence of amoebiasis in any given population exposed to the risk of infection by Entamoeba histolytica. Local (Ibadan) strains of Entamoeba histolytica have been successfully cultured and the in-vitro characteristics studied. From the materials provi.ded by the in-vitro cultures of the organism, investigations have been made on E. histolytica antigens and the corresponding antibodies produced in man. The results of these investigations have been utilized in immunological studies, designed to define the mechanism of production of some of the problems posed by amoebic infections. The severity and high fatality of the disease in pregnancy and puerperium, was studied in detail. The observation that amoebiasis tends to be more severe and to have a higher mortality in pregnant and puerperal women was made only recently. At the time the present studies were planned, the association of pregnancy with severe amoebiasis had not been well established, and the mechanism for this association was unknown. It was, however, wall known that pregnant women were more liable to severe for-ms of certain other infectious diseases and it was considered possible that a similar mechanism might be operating in the case of amoebiasis. The present work confirms these clinical observations. Thus from the statistical analyses of the results of both the autopsy and prevalence studies, it became evident that the high fatality of amoebiasis during pregnancy and the early puerperium was not fortuitous but real. A fulminating type of lesion affecting the whole length of the large bowel is commoner in pregnant women and in those in the early puerperium dying of amoebiasis, than in any other cases of amoebiasis seen at autopsy. Furthermore, the biochemical and immunological studies help to throw some light on the mechanism of the selectivity of Infection by E. histolytical. These same results, also provide some explanation for the severity of amoebiasis during pregnancy and the allied states. The conclusions, support the hypothesis of lowered resistance to infectious diseases during pregnancy. Speculative submissions are, therefore, made on the defective immune mechanism occurring during pregnancy and the early puerperium. Thus, the inability of pregnant women to produce 'sufficient antibodies' to amoebic infections, demonstrated by the reactivity of the immunoglobulins in amoebiasis, confirms the suspicion of the existence of a derangement of host-defence mechanisms during pregnancy. This raises the hope and encourages future search for the specific serum agents) which may account for the deranged immune mechanism. On similar basis, the characterization of amoebic antigens together with that of the corresponding antibodies, offers a new field in the study of the immunopathology of amoebiasis. In conclusion, from the combined autopsy, prevalence, in-vitro experimental, biochemical, and immunological studies, it is submitted: 1. That the association of pregnancy with the severe form of amoebiasis at least, in this part of the world, is one of the perplexing problems posed by the disease. 2. That chronic amoebic infection is associated with the development of growth-inhibiting factors in the serum, for example, in patients with amoebic liver abscess. 3. That, on the contrary, growth promoting factors were demonstrated in the sera of pregnant/puerperal women with or without acute amoebic dysentery. 4. It is suggested that the severity of the disease in pregnant/puerperal women is a reflection of the derangement of immune response during pregnancy, with particular reference to the production of serum immunoglobulins. 1 results 1
- H5N1 Virus. 1 results 1
- HPAI. 1 results 1
- Nigeria experienced outbreaks of Highly Pathogenic Avian Influenza (HPAI) H5N1 virus in poultry between 2006 and 2008. Mixed poultry rearing have been postulated as factors responsible for easy spread, while inadequate diagnostic specimens and procedures have militated against prompt diagnosis of the disease. This study was designed to elucidate the comparative susceptibility and diagnosis of H5N1 virus infection in chickens and ducks. Clinical and pathological examinations, agar gel immunodiffusion and viral isolation were used to confirm 468 suspected chickens, ducks, turkey and geese from six (6) geopolitical zones submitted to the reference laboratory at National Veterinary Research Institute, Vom. Spatial data were mapped with Arc-view GIS. Fifty-six of the 80 confirmed H5N1-positive backyard poultry cases were compared for proportions (single and mixed species); the association was calculated by odds ratio using MedCalc Software. Immunohistochemistry (IHC), Real-time Reverse Transcriptase-Polymerase Chain Reaction (RRT-PCR), sequencing and alignment using the haemagglutinin cleavage site were used to detect and characterize H5N1 in Formalin-Fixed Paraffin-Embedded (FFPE) chicken tissues from ten of the outbreak cases. Comparative pathology; tissue virus predilection and titre were carried out using IHC and RRT-PCR in 10 Muscovy, 10 Pekin and eight Mallard 3-weeks old specific pathogen-free ducks each separately experimentally infected with clade 1 or 2.2 H5N1 virus genotypes. Twelve age-matched chickens served as in-contact sentinels. Clinical signs, lesions and mortalities were severe in older birds, while younger and free-range chickens showed minimal clinical signs and lesions. Lesions were multi-systemic and characterized by severe haemorrhages and necrosis. Mortalities in birds were: 20.6% (north-central), 16.5% (north-east), 15.9% (north-west) and 6.0% (south-west). Wetland areas in north-west and north-east had more positive cases. There were higher risks (OR=3.02) of infection and mortalities in mixed than in single species farms. H5N1 RNA virus detection in FFPE tissues was successful in 7 of 10 while gene sequencing was possible only in four. All the viral RNA characterized belonged to the sub-clade 2.2 with >96% homology to similar virus of European origin. Along the 154 nucleotides sequenced, amino acid exchange (mutation; Ala →Thr) occurred at position 544. Clade 1-infected Muscovy ducks shed more viruses, showed more severe nervous signs and mortality than Pekin and Mallard. Pekin ducks were moderately susceptible to clade 1 but insusceptible to clade 2.2. Mallard ducks were resistant to clinical disease from both viruses. Chickens exposed to infected ducks had 100% mortality four days post-exposure. Eyelids, combs, wattles, thymus, spinal cord, pancreas, cerebrum and bursa of Fabricius had higher RRT-PCR detection than the heart, lung, trachea, liver, spleen and intestine traditionally harvested for HPAI- H5N1 antigen detection. Co-rearing of Muscovy ducks with chicken posed greater risk of transmission of Highly Pathogenic Avian Influenza to the latter. Detection of H5N1 virus in formalin-fixed paraffin-embedded chicken tissues was an important finding useful in retrospective diagnosis of HPAI. 1 results 1
- Poultry, 1 results 1