Malignant Catarrhal Fever (MCF) (Snotsiekte – Africa, Malignant head catarrh, Catarrhal fever, Gangrenous coryza)
Description The African form of malignant catarrhal fever is due to alcelaphine herpesvirus-1. This virus is carried by wildebeest and the disease in cattle is often known as wildebeest-associated malignant catarrhal fever. This virus is not found in the North American or European form of the disease except in exotic ruminants in zoos. Malignant catarrhal fever in North America, Japan and Europe is usually sporadic although epizootics have been reported. It is characterized by a necrotizing arteritis affecting many body systems. Affected cattle usually die within a week of onset of signs but some animal survive for extended periods with a chronic disease or recovery. The agent of this form of malignant catarrhal fever is classified as ovine herpesvirus 2 (OvHV-2); subclinical bovine infection with the virus can occur. There are rare reports of necrotizing vasculitis associated with OvHV-2 in goats. Sheep are carriers of this form of malignant catarrhal fever and are often responsible for spreading the disease to cattle.
Most affected cattle may have the following signs: fever, depression, diarrhea, anorexia, rhinitis with nasal discharge that becomes mucopurulent and encrusted. The skin of the muzzle becomes eroded, and there is stomatitis, pharyngitis, laryngitis, and parotitis with salivation. After a short febrile period; most cattle with the severe disease die within 10 days.In addition to the lesions referred to the above, there may be edema of the meninges, perivascular cuffing in other areas of the brain, enteritis, general lymphoid hyperplasia, and corneal opacity. Gray foci may be seen in the kidneys and liver. The anterior cervical and retropharyngeal lymph nodes may be hemorrhagic and edematous. Vasculitis is widespread.Acute MCF cases caused by ovine herpesvirus-2 and alcelaphine herpesvirus-1 are similar clinically and pathologically. Disease course may range from peracute to chronic. Cases in deer are often peracute with sudden death. Deer that survive for a few days and bison usually develop hemorrhagic diarrhea, bloody urine, and corneal opacity before expiring. High fever (106-107F [41-41.5C]) and depression are common. Other signs that may be present include catarrhal inflammation; erosions and mucopurulent exudation affecting the upper respiratory, ocular, and oral mucosa; swollen lymph nodes; lameness; and CNS signs (depression, trembling, hyporesponsiveness, stupor, aggressiveness, convulsions). Historically, MCF has been described as having several ‘forms’mild, peracute, head and eye, intestinal, etc. There is little basis for this division and it is of little utility. Variation in organ system involvement sometimes can be seen in the same outbreak, and is at least partially related to survival time after disease onset. On average, the time to death in European cattle breeds is somewhat longer than in deer, bison, water buffalo, and Bali cattle. In cattle, swollen lymph nodes and severe eye lesions (panophthalmitis, hypopyon, corneal erosions) are more frequent, and hemorrhagic enteritis and cystitis less frequent, than in deer and bison. Skin lesions (erythema, exudation, cracking, crust formation) are common in animals that do not succumb quickly. Up to 25% of cattle experience chronic disease, and sometimes the disease waxes and wanes. Most eventually die, but ~5% clinically recover. Hematologic parameters are not rewarding. In a few outbreaks, the goat MCF virus (caprine herpesvirus-2) induced disease in white-tailed and Sika deer. These cases were subacute to chronic, with weight loss, dermal inflammation, and alopecia as the primary signs. Whether this strain of virus causes disease in species other than deer is not known.
- Incubation: 9 – 44 days
- Morbidity is low and mortality is high
- Increased temperature
- Bilateral ocular and nasal discharges
- Dyspnea and cyanosis 6. Loss of appetite
- Encrustation of muzzle and eczema of the perineum, scrotum and udder
- Erosions on the lips, tongue, gums, soft and hard palate
- Swollen reddened eyelids, corneal opacity and conjunctivitis (Fig.)
- Photophobia associated with corneal opacity and blindness
- Reluctance to swallow because of oesophageal erosions and drooling
- Enlarged body lymph nodes
- Rarely, uncoordinated movements and shivering