Sporadic bovine encephalomyelitis

From Cow
Chlamydophila pecorum under light microscopy
Fibronous serositis in an experimentally-infected calf

Sporadic bovine encephalomyelitis (SBE) is a neurological disease of cattle worldwide, caused by the bacterium Chlamydophila pecorum[1].

Cause

Chlamydophila pecorum is a bacterium which is spread by physical contact between cattle and via fomites[2].

Subclinical intestinal infections in cattle and other animals may be the source of infection in SBE. The disease is most often seen in calves <6 mo old and rarely in older cattle. Morbidity rates are usually low but can reach 50%; many sick calves die if not treated at an early stage.

Clinical signs

Presenting clinical signs, often seen in yearlings, occur 6 - 30 days post-infection. Signs, which worsen over a 10 - 14 day period, include anorexia, diarrhoea, fever, lethargy, ptyalism, neurologic signs, polyserositis, abortion, conjunctivitis, non-suppurative meningoencephalomyelitis[3], enteritis, pneumonia, and polyarthritis[4]. In calves, stiffness may be evident, with knuckling at the fetlocks. Incoordinated and staggering may also occur.


Diagnosis

A tentative diagnosis can be based on clinical signs and particularly on the presence of serofibrinous peritonitis in the absence of other causes of peritonitis such as intestinal volvulus, intussusception, traumatic perforation of the reticulum, perforated abomasal ulcer, or displaced organs. Differential diagnoses also include rabies, infectious bovine rhinotracheitis with encephalitis, listeriosis, thromboembolic encephalomyelitis, polioencephalomalacia, pseudorabies, paramyxovirus encephalomyelitis, and malignant catarrhal fever. A diagnosis of SBE is confirmed by isolation of the organism from brain tissue in either developing chicken embryos or cell cultures, by histologic changes in brain sections, by evaluation of tissue impression smears after Giemsa or immunofluorescent staining, or by demonstration of Chlamydophila DNA via PCR testing.

Post-mortem of euthanased cattle include serofibrinous peritonitis, pleuritis, and pericarditis are common and are especially pronounced in more chronic cases. Histopathology often reveals microscopic lesions in the brain consisting of perivascular cuffs and inflammatory foci in the parenchyma composed primarily of mononuclear cells.

Differential diagnoses would include bracken fern poisoning, rabies, BSE and Akabane virus infection.

Treatment

Antibiotics which are effective against Chlamydophila pecorum include tetracyclines, oxytetracyclines, and tylosin. Oxytetracyclines, the drug of choice, is given at 10 – 20 mg/kg/day for 10 - 14 days.

High doses appear to be more effective If treatment is effective, the fever should drop significantly within 24 hr. No vaccines are available.

References

  1. Kaltenboeck B et al (2009) OmpA and antigenic diversity of bovine Chlamydophila pecorum strains. Vet Microbiol 135(1-2):175-180
  2. Harshfield GS (1970) Sporadic bovine encephalomyelitis. J Am Vet Med Assoc 156(4):466-77
  3. Theil D et al (1998) Neuropathological and aetiological studies of sporadic non-suppurative meningoencephalomyelitis of cattle. Vet Rec 143(9):244-249
  4. Merck Vet Manual