PATHOLOGICAL AND MOLECULAR DIAGNOSIS OF SHEEP POX
Loading...
Date
2015-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
SRI VENKATESWARA VETERINARY UNIVERSITY, TIRUPATI - 517 502 (A.P) INDIA.
Abstract
ABSTRACT :
Sheep farming is the major source of livelihood for landless poor in
India. Pox infection in sheep causes a huge economic losses in the Indian
subcontinent in terms of poor hide quality, decreased productivity, abortions
and even mortality in lambs. Hence, the present study was undertaken to
describe the gross and histopathological changes in affected organs and to
study the ultrastructural changes in skin and lung and also to confirm the
disease by PCR. Sheep pox is caused by SPPV, a member of the genus
Capripoxvirus and family Pox viridae. In the present study a total of 1240
sheep (Nellore Dora breed) of both sex and different age groups from various
slaughter houses and field were screened for clinical signs/ lesions of sheep pox
and of these, 77 animals were found affected (including both ailing and dead)
with an overall incidence of 6.2%. Among 77 affected sheep, detailed necropsy
was carried out in 16 animals and the representative tissue samples were
collected for further studies. A few skin/scab samples from ailing animals were
also collected at random for PCR studies.
Clinically, the ailing animals showed rise of body temperature, occulonasal
discharges and characteristic cutaneous pox eruptions at different stages
of development. The symptoms were more severe in young lambs.
At necropsy, gross lesions of sheep pox were predominantly seen on the
skin and lungs followed by other internal organs. The skin lesions were
characterized by papules, nodules and scabs mostly on wool-less parts of the
body. The papules were greyish white, circular, hard that coalesced to form
white and firm nodules with ulcerated centres. Some papules were encrusted to
form the scab. The affected lungs were edematous and congested with irregular
areas of consolidation besides rib impressions on surface. A few macules and
numerous papules/nodules were noticed along with a very few pustules. Round
and white papules were seen on the tongue, rumen, and reticulum. Liver,
kidney, heart and spleen showed small, white and circular necrotic areas.
Lymph nodes were enlarged and edematous.
In the present study, microscopic lesions were noticed in the skin, lungs
and in other internal organs like tongue, rumen, reticulum, liver, kidney, heart
and spleen. Sections of skin showed hyperkeratosis, acanthosis, parakeratosis,
hydropic changes with microvesicle formation and presence of eosinophilic
intracytoplasmic inclusion bodies in epidermal layer. In the dermis folliculitis,
vasculitis, presence of SPC’s and infiltration of mononuclear cells and
fibroblasts were seen. In the lungs, congestion, focal areas of necrosis,
proliferative alveolitis, foetalization, thickened interalveolar septa with
infiltration of mononuclear cells were seen. The alveolar lumen revealed
eosinophilic amorphous material and presence of sheep pox cells with
eosinophilic intracytoplasmic inclusion bodies. Proliferative bronchiolitis and
peribronchiolar lymphoid aggregations were the other changes observed in
affected sheep.
The sections of tongue revealed congestion, ulcerations and formation of
microvesicles. In the rumen, hyperkeratization, necrosis of squamous epithelial
cells and presence of characteristic cytoplasmic inclusions in the prickle cells
were seen. Reticulum revealed necrosis, sloughing of squamous epithelium
with presence of eosinophilic intracytoplasmic inclusion bodies. Sections of
liver showed sinusoidal dilatation, presence of inclusion bodies in few
hepatocytes and formation of new bile ductules. The kidney sections showed
interstitial nephritis, presence of hyaline casts, eosinophilic intracytoplasmic
inclusion bodies in the tubular epithelium and necrotic foci. Sections of heart
revealed haemorrhages and infiltration of lymphocytes in between the muscle
fibers. Depletion of lymphocytes in the lymphoid follicles was seen in the
spleen and lymph nodes of pox affected sheep.
In the present study, the ultrastructural changes were studied in the skin
and lung tissue samples by TEM. The skin revealed hydropic changes and
presence of numerous electron dense particles suggestive of immature virions.
In the lung, proliferation of type II pneumocytes, presence of the immature
virus particles in affected alveolar epithelial cells and macrophages, thickened
interalveolar septa along with nuclear and chromatin changes were seen.
The virus suspension from skin papule/ nodule was passaged thrice in
embryonated eggs through CAM route that revealed death of embryo as early
as 48 hours PI. Grossly, congestion, edema, hemorrhages and necrosis and
microscopically congestion were noticed in the CAM.
In the present study, molecular diagnosis of pox by PCR was carried out
with skin and lung samples from affected sheep using B68 and B69 primers
specific for P32 gene of Capripoxvirus that yielded an amplified product of 390
bp, confirming the Capripoxvirus infection in the samples tested.
The present study revealed the gross, histopathological and
ultrastructural lesions in different organs in natural cases of sheep pox. Further,
the disease was confirmed based on the pathological and molecular diagnosis
of Capripox infection in the affected sheep in the study area.
Description
THESES
Keywords
SHEEP ; Pox infection; SPPV; MOLECULAR DIAGNOSIS