Chlamydophila pecorum: Clinical
Encephalomyelitis.
This disease is characterized by a systemic chlamydial infection, with several
organs involved, most notably the nervous system. Recovery depends on the extent of
central nervous system involvement (Perez-Martinez and
Storz, 1985). Clinically, progressive weakness leads to paralysis,
with death in 60% of affected animals 10-14 days after the onset of signs. The
disease may remain enzootic , leading to outbreaks in newly introduced cattle
(Harshfield, 1970). Schachter et al. (1975) showed
by serotyping that a chlamydial strain associated with sporadic bovine encephalomyelitis (SBE) was
distinct from strains associated with chlamydial abortion in cattle. C. pecorum strain ATCC
VR-628, originally isolated from the brain of a calf with SBE (McNutt and Waller,
1940), was proposed as the type strain
for the species.
Pneumonia.
Chlamydia-induced pneumonia in sheep was described as an interstitial bronchopneumonia
, spreading from the bronchioles to the lung parenchyma (Dungworth and Cordy,
1962). White (1965) was able to experimentally produce chlamydial pneumonia in young calves with
a chlamydial isolate obtained from calves with pneumonia (Harbourne,
1966).
Calves with pneumonia have a serous, mucous or mucopurulent nasal discharge, are
febrile and depressed, with a dry cough and dyspnea.
Usually the animals recover, but some remain chronically debilitated (Storz,
1971).
Polyarthritis.
This disease has been described in sheep (Storz et al.,
1963) and calves (Storz et al.,
1966) in the USA.
In sheep, it presents as a seasonally influenced syndrome, characterised by fever, stiffness, lameness, anorexia and, frequently, conjunctivitis.
Infection of the synovial tissues and associated inflammation of limb joints leads to stiffness and lameness, but joint enlargement is not usual except in long-term cases. Most lambs will overcome their stiffness with forced exercise.
In cattle affected by polyarthritis due to C. pecorum, the disease is more serious and mortality is high. Infected calves are weak and stiff. Fever and diarrhoea may result. Joints, which may be grossly enlarged, are painful on palpation. Death may occur 2-10 days after the appearance of clinical signs
(Storz et al., 1966).
Conjunctivitis.
In sheep, chlamydial organisms have been recovered from cases of follicular
conjunctivitis
(Storz et al., 1967) and keratoconjunctivitis
(Dickinson and Cooper, 1959). These conditions may occur in association with pneumonia or polyarthritis and may reflect localized or systemic infection. In lambs with conjunctivitis, 10-85% were found to have polyarthritis
and, conversely, nearly all lambs with polyarthritis had conjunctivitis.
Early signs of chlamydial conjunctivitis in sheep included
chemosis and dilation of conjunctival vessels. As the disease progresses, abundant seropurulent eye discharge is seen,
sealing the eyelids in a crust. Severe inflammatory involvement is followed by neovascularisation of the
cornea [new blood vessel formation], with both eyes equally affected in the majority of lambs
(Stephenson et al., 1974). In uncomplicated cases, the disease is self-limiting,
with full resolution of lesions.
Cattle affected by polyarthritis and pneumonia
may also have conjunctivitis (Storz, 1971). Chlamydial isolates have been recovered from
bovine keratoconjunctivitis cases (Dyml, 1965).
Enteritis.
The intestinal tract may be the natural habitat for certain chlamydial
[presumably C. pecorum] strains (Storz,
1971). However,
intestinal infections may be overlooked as they are often asymptomatic, both in sheep
(Wilson and Dungworth, 1963) and cattle (Wilson,
1962; Perez-Martinez and Storz, 1985). In lambs with intestinal infections, diffuse proliferation of intestinal lymphoid tissue and enlargement of the mesenteric lymph nodes were associated with a marked thickening of the terminal
ileum
(Piennar and Schutte, 1975).The shedding of infectious chlamydiae in faeces is likely to be an important means by which infections are spread in
animals [see: C. pecorum: epidemiology].
Stressing of carrier animals may precipitate chlamydial shedding and the onset of
overt disease (Storz, 1971).
In cattle, intestinal infection with chlamydiae may result in diarrhoea in calves, in which the mucosa of the entire intestine may be congested and
petechiated
(Doughri et al., 1974). Chlamydiae have
also been isolated from the faeces of clinically normal calves (Wilson,
1962; Wilson and Dungworth, 1963).
Metritis and infertility.
In cattle, the ability of C. pecorum
to cause endometritis
has been demonstrated experimentally. Approximately 2-3 days after the inoculation
of C. pecorum, the cows were depressed and anorexic,
with a thick, yellowish vaginal discharge (Bowen et al.,
1978; Wittenbrink et al.,
1993). In some cases, a moderate, chronic endometritis developed. At necropsy, the uterus was filled with a
purulent exudate. Cattle infected with C. pecorum
had reduced fertility. In cattle experimentally infected with C. abortus strains, a sub-acute
metritis developed
which was less severe than that seen with C. pecorum. A serological survey of chlamydial antibody in cattle showed higher CFT titres in 2326 aborting cows compared to 1310 normally calving animals
(Wilsmore and Dawson, 1986), [MEW
Comment: presumably mainly due to C. abortus].
NEXT: C.
pecorum: Laboratory Diagnosis
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