EVOLUTION

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SPECIAL SECTION

Viral Disease - Malignant Catarrhal Fever

Synonyms

Bovine malignant catarrh

Definition

It is an acute highly fatal infectious disease of cattle characterized by catarrhal and mucopurulent inflammation of eyes and nostrils, erosions of nasal mucosa, rapid emaciation and enlargement of lymphnodes, corneal opacity and nervous symptoms

Etiology

Gamma - Herpes virus (lymph trophic)

Epidemiology

Highly fatal disease of wild ruminants and cattle and farmed deer and occasionally pigs. Disease associated with contact with sheep, often lambing ewes, and in Africa also with wildebeest calves. Disease may occur sporadically or in outbreaks

Incidence

Worldwide, reported in India also

Transmission

In Africa - wild beasts carry the virus and transmit to cattle

In US - sheep carry the virus and transmit to cattle

Not transmissible between infected cattle

Clinical signs

High fever 106˚ - 107˚ F

Catarrhal conjunctivitis and rhinitis

Mucopurulent discharge from eyes and nostrils

Exudate flows from eyes and nostrils and soon dries and sticks

Eyes are sensitive to light

Corneal opacity

Emaciation

Erosions in skin of muzzle, roof of mouth and cheeks

Diarrhoea

Nervous signs in later stages

In mild disease skin lesions like thickening and peeling of skin in axilla, perineum and neck are seen

Lymphnodes swollen - form small subcutaneous nodules, form a chain around the jugular groove of neck

GROSS LESIONS

Lymphnodes are swollen; cut surface is granular

Erosions in nasal, oral and pharyngeal mucosa covered by mucopurulent exudate

Congestion, edema and erosions in esophagus, rumen, reticulum and omasum

Erosions and ulceration in abomasum

Hyperemia and edema in small intestine

Congestion and edema in eye

Enlarged and mottled liver and kidney

Renal cortex contain grey to white foci resembling infarcts

Cooked up appearance in brain

Microscopic Lesions

Lymphnodes

Dilation of lymphatic channels, severe oedema and proliferation of reticulo - endothelial cells and lymph nodes

Blood Vessels

Perivascular and intramural infiltration of mononuclear cells

Medial necrosis and endothelial swelling of arteries and arterioles

Oral/Nasal Epitheliumh2>

Necrosis and lymphocytic infiltration

KIDNEY

Collection of mononuclear cells in the cortex

BRAIN

edema and lymphocyte infiltration in meninges, perivascular cuffing in medulla, pons, hippocampus, cerebrum, cerebellum & spinal grey matter

No inclusion bodies or syncytia is seen

Diagnosis

Lymph trophic nature of virus; virus is associated with lymphocytes; no free virus is detectable in tissues of cattle

Main pathological features are lymphocytic proliferation and infiltration with vasculitis

ELISA, serum neutralization test, immunofluorescence test and by pcr.

Differential diagnosis from Rinderpest based on prominent intestinal lesions , mucosal disease, and infectious rhino tracheitis.

Treatment

Supportive treatment can be given, non-steroidal anti-inflammatory will ease the discomfort

Prevention and Control

Inactivated or live vaccines with suitable adjuvants induce antibodies against MCFV.

In the absence of a vaccine, the only effective strategy is to limit contact between MCF susceptible species and the natural hosts of the virus.

Sheep has been considered as a spreader of field outbreaks. Therefore, rigid separation of cattle from sheep is suggested.

The feed used by ewes and lambs should not be provided to cattle.

Avoid contact between reservoir host (wildebeest and wild rabbits) and cattle


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