Ephemeral Fever

Syn: 3-day sickness, stiff sickness, Bovine epizootic fever

• It is arthropod borne non-contagious viral disease of cattle characterized by high fever, stiffness, lameness and muscular tremor.
• It is mostly seen during rainy season and most of recovered cattle have lifelong immunity.
• All breeds of cattle are found to be susceptible of this disease, also recorded in both indigenous and exotic breeds along with water buffaloes.

Etiology:

• Bovine ephemeral fever virus, Genus; Ephemerovirus
• Family: Rhabdoviridae
• Enveloped virus with surface glycoprotein spikes
• Ss-RNA, -ve sense

Epidemiology:

• Disease is found in Africa, Australia, Asia. It was first recorded in Central Africa in 1867.
• It is widely reported from India, Pakistan, Palestine, Indonesia, Sumatra, Japan, Papua New Guinea, Turkey and Cyprus
• Virus is bullet shaped in nature belonging to Rhabdoviridae.
• Virus becomes ineffective at 37°C at 17 hours or at 25°C at 120 hours.
• Virus is sensitive to ether. It is inactivated at pH 2.5-9.1
• It typically occurs during warmer months with outbreaks often linked to periods of high rainfall that favor vector populations.
• Younger animals may be less susceptible to severe disease than older animals but all ages can be affected.
• It has huge economic impact from decreased milk production, loss of condition in beef cattle, and loss of draught animals.
• In typical case, disease runs from 3 to 4 days, a circumstance which has given the title of 3 days sickness.

Transmission:

• Transmitted by sand-fly, mosquitoes
• Sometimes by vaccination or by IV inoculation
• It donot spread by close contact, body secretions including semen or aerosol (droplets).

Pathogenesis:

• Cattle bitten by vector (sandflies/mosquito)
• Entry of virus inside host
• Virus reaches to blood circulation and produces viremia but stays fixed in mucus membrane of GI tract and buccal cavity.
• Viremia
• Localization in mesodermal tissues of joints, muscles, LN
• Dyspnea and stiffness of limb

Clinical Findings:

• Incubation period of disease ranges from 2-10 days
• Sharp rise of temperature ranging between 103-107°F or more. It is intermittent in some cases.
• Shivering, trembling
• Affected animals disincline to move and if forced to move, they move with great difficulty with arched back condition.
• Marked anorexia, decreased milk production
• Salivation, nasal secretion and lacrimation
• Shifting type of lameness; i.e. from one leg to another
• Suspension of rumination, grinding of teeth
• Aspiration pneumonia
• Initial constipation followed by diarrhea
• Muscles of affected limb becomes stiff, hard and painful

PM Findings:

• Animals seldom die. So, postmortem is not warranted.
• Animals shows enlargement and edema of lymph nodes.
• Joints may contain serofibrinous deposition leading to synovitis, tendovaginits, and periarthritis.
• Congestion of lungs and pleura.
• Necrotic changes of skeletal muscles.
• Pericardial sac may contain blood.
• Enlargement of lungs

Diagnosis:

• Based on clinical findings
• Based on PM findings
• Isolation and identification of virus
• Complement fixation test, FAT, AGID, ELISA
• Blood counts: Neutrophilic leukocytosis

Differential Diagnosis:

1. Milk fever:

• Disease occurs in 3 different stages; excitement- sternal recumbency- lateral recumbency

2. Laminitis:

• Local inflammation and lameness of concerned feet.

Treatment:

• No specific treatment
• Broad spectrum antibiotics to control secondary infection; Tetracycline @1ml/10 kg, b.wt. IM X OD X 5-7 days
• Novalgin @15-20 ml IM for 3 days
• Complete rest of affected animals, good care and nursing of animals is likely recommended.
• Drenching of fluids and drugs should be avoided.
• Calcium borogluconate may be administered in recumbent cattle.

Control Measures:

• Control of vector
• Vaccination; Two-part vaccine with freeze dried and liquid components that must be mixed. Two injections of vaccine 2 weeks-6 months apart under skin of neck. Immunity: 1 year