MALIGNANT CATARRHAL FEVER (MCF)

By ZarreenSajjad,

DVM Student, Faculty of Veterinary Sciences,

University of Agriculture, Faisalabad.

Synonyms used for MCF areMalignant Catarrh, Malignant Head Catarrh,Gangrenous Coryza,and Catarrhal Fever.MCF is an acute,highly fatal infectious disease of cattle characterized by catarrhal and mucopurulent inflammation of eye,nostril,and erosive lesions in the oral mucosa.

o ETIOLOGY

Classification of the causative agent:Malignant catarrhal fever is caused by a virus,as it belong from virus familyHerpesviridae,subfamily Gammaherpesvirinae,genusRhadinovirus.

The MCF subgroup of viruses,called MCFVor type 1 RuRV, contains at least 10 members,five of which cause disease to date.

1) Wildebeest associated MCF: alcelaphine herpes viruse 1 (AIHV-Endemic in wildebeest populations worldwide

2) Sheep associated MCF: ovine herpesviruse 2 (OvHV-2).Endemic in most sheep populations worldwide.

3) Caprine associated MCF:caprine herpesviruse 2(CpHV-2).Endemic in most domesticated goat population worldwide,and causes MCF in cervids.

4) Unknown origin:MCF in white tailed deer (MCFV-WTD)

o EPIDEMIOLOGY:MCF is generally fatal disease of cattle and many other species of Artiodactyla,which are infected either by AIHV-1 or OvHV -2 .The AIHV -1 and OvHV -2 can give rise to epizootics. Clinical infection occurs in member of familiesBovidae,Cervidae and Giraffidae.Animalsthat develop MCF are usually dead end host.

AIHV-1 Transmission in wildebeest occursperinatal, all calves become infected within the first few

months of life and remain carriers for life. Transmission to susceptible host occurs only from wildebeest,there is no definitive evidence

that MCF affected animal transmit the disease horizontally.

OvHV-2 A proportion of lambs are infected in utero with most lambs becoming infected perinatal. Transmission is only from sheep to susceptible host, not horizontally between infected hosts.

MCFV has been isolated from other exotic ruminants with unknown disease potential;ibex,musk ox,gemsbok,topi and antelope.Only AHV-1 has been isolated and characterized;OvHV -2 has consistently proved impossible to isolate using conventional methodologies and has been identified by applying molecular technology to detect the viral DNA.

o Transmission:

AIHV-1: Transmission of AIHV-1 with in free living wildebeest population is

very efficient;all wildebeest calves are infected within first few months i.e. 1-2 months of life by in utero,direct contact or aerosol route. Contamination of pastures may also contribute to transmission.

Transmission after 6 months of age is rare. Close contact is usually needed but transmission over 100 meter has

been reported. Congenital transmission of AIHV-1 within infected domestic cows

can occur with varying disease latency periods in newborn calves.

OvHV -2: Transmission is mainly by respiratory route ,probably in aerosols The proportion of lambs are infected in utero with most lambs

becoming infected perinatal.Infection may not occur till after 3 months of age.

Close contact with sheep by susceptible species is usually required,but case has been reported when sheep and cattle were separated by 70 meters,and in bison herds up to 5 km from a lamb feedlot

There is a wide spectrum of susceptibility:Bos Taurus and Bosindicus cattle are relatively resistant to OvHV-2 and cases are usually sporadic.

o Clinical signs:The clinical sign of MCF are variable and range from per acute to chronic.

Gross pathological changes are generally widespread and may involve most organ systems. The severity of this disease does vary, and signs include:

o Per acute:either no clinical sign are detected or depression followed by diarrhea to dysentery may develop 12-24hours prior to death

o Progressive bilateral corneal opacity,starting at the periphery is characteristic.

o Cooked brain appearanceo Nervous sign such as hyperesthesia,incoordination, nystagmus

and head pressing may occur alone or with other sign of MCF,o severe inflammation of the oral and nasal mucosa;o bleeding and inflammation of stomach and small intestine

(hemorrhagic gastroenteritis);o fever;106-107Fo diarrhea; depression,dyspneao redness of oral and nasal mucosa with accompanying

discharges;o encrustation of the muzzle and nasal area, causing obstruction

of the nostrils and shortness of breath, open-mouthed breathing, and drooling;

o skin lesions occasionally are seen, and horn as well as hooves wall may be loosened or sloughed;

o clouding or ulceration of the eyes.(catarrhal conjunctivitis)o Terminal stages CNS symptoms: falling, circling, headpressing,

high stepping, convulsions and finally death.

Principal lesions Nostril –respiratory system Oral mucosa Eye Lymphnodes

Lessprominently in the intestinal tract Brain Erosions and hemorrhages in gastrointestinal tract contents may be

hemorrhagic Enlarge lymphnodes ,but degree varies oftenfirm and white on cross-

section,but submandibular and retropharyngeal may be hemorrhagic and even necrotic

Cattarhal exudate,erosions and diphtheritic membranes often observed in the respiratory tract.

Urinary bladder often has characteristic echymotic hemorrhages of the epithelial lining

Renalcortex may have multiple raised white foci, each 1-5 mm in diameter,often with a thin zone of hemorrhage.

In the absence of molecular diagnosis,histological changes are often relied on for diagnosis of MCF and are characteristic;epithelial degeneration,vasculitis,hyperplasia and necrosis of lymphoid organs and widespread interstitial accumulation of lymphoid cells in non lymphoid organs.

Enlarge pre scapular lymph node MCF;lung perivascular lympho-plasmacytic cuffing and vasculitis.

Marked perivascular inflammation.

o Laboratory diagnosis AIHV-1 may be recovered from clinically affected animal using peripheral blood leukocytes or

cell suspensions prepared from lymph nodes and spleen .Virus can also be recovered from wildebeest,either from peripheral blood leukocytes or from cell suspension of other organs

OvHV-2 has never been identified formally,although lymphoblastic cell line propagated from affected animals contain OvHV -2 specific DNA and virus particles have been observed in these cells.

Both OvHV-2 and AIHV-1 have been transmitted experimentally to rabbits and hamsters which develop lesion characteristic of MCF

Polymerase chain reaction is becoming the method of choice for diagnosing OvHV -2 form of the disease.

o Serological tests

AIHV-1 Infected wildebeest develop antibody to AIHV-1 ,which can be detected in four assays below Virus neutralization Immunoblotting Enzyme linked immunosorbent assay (ELISA)

Immuno-fluorescence

OvHV-2 Antibodies to OvHV -2 has only been detected by using AIHV-1 as the source of antigen.These

antibodies are detected by Immunofluorescence ELISA immunoblotting