CHLAMYDIAL INFECTIONS
Although less frequent in cattle than in sheep, Chlamydia infections can cause
reproductive disorders in cows and bulls, and incidents have been recorded in
Europe since the 1970's (Polak et al., 1984).
Recognised for some time as the cause of epidemic abortion in cows in the USA,
Chlamydia psittaci is associated in Europe with sporadic abortion (at 3 to
7 months) due to necrotic placentitis and a direct effect on the fetus (producing
liver lesions). Jaskowski (1973) and Jahn et al. (1972) also describe infertility with
vaginitis and endometritis.
In the bull the infection results in balanoposthitis, inflammation of the vesicular
gland (seminal vesiculitis) and above all orchitis. Several outbreaks have been
reported in Europe (Poland, Czechoslovakia) and investigated by Jaskowski et al.
(1980) and Rob and Rozinek (1976). Chlamydia can contaminate the semen of
infected bulls, but in an irregular, intermittent and feeble way. Guérin (1983) succeeded
in isolating C. psittaci only once from 8 ejaculates of one bull, and once
from 12 ejaculates of another; the semen of two other infected bulls was constantly
negative. At the same time all cultures performed with 134 doses of frozen semen
from 10 bulls gave negative results. This demonstrates the difficulty of isolating
Chlamydia in low concentration from semen. The presence of proteases means that
the semen has to be diluted 1:10, further decreasing the already low concentration
of the organism. It is also difficult to recover the organism from diluted, frozen
semen because of the presence of antibiotics in the diluent, which are toxic for
Chlamydia in the concentrations normally used.
There is little information on transmission from male to male, and the conditions
required for disorders to occur, although the oral route of infection seems to
be the commonest, supplemented by indirect transmission through tick bites. Experimental
transmission of the disease is difficult, even when strains of Chlamydia
from clinically infected animals are used. Chlamydia may occur in the semen of clinically
healthy bulls.
Insemination of a cow with contaminated semen may lead to disorders (infertility
with vaginitis and endometritis), but it has not yet proved possible to establish
the amount of an infective dose, or a suitably receptive substrate.
Diagnosis is relatively easy in the case of abortion, by means of bacteriological
examination of the liver of the aborted fetus (stained smears and culture in
embryonated eggs). Isolation from bull semen is difficult. Spencer et al. (1983) described
a transport medium to aid the isolation of Chlamydia from samples, capable
of preserving the organisms for 30 days at room temperature and 34 days at + 5°C.
The serological technique generally used is complement fixation, but it is difficult
to interpret the titres obtained, since they are often low and of limited persistence
(a few weeks). The test may also detect antibodies to Chlamydia intestinalis
(a non-pathogenic saprophyte) in addition to C. psittaci. Complement fixation
enables a herd diagnosis to be made, but cannot be used to diagnose individual
cases.
Recommended treatment is by antibiotics (tetracycline or chloramphenicol), but
it is uncertain if they are sufficiently effective and safe to use on bulls (possible
adverse effect on semen production). In cows, daily injection of 3-5 g of tetracycline
for 4-5 days prevented abortion in pregnant cows in contact with a cow which
had aborted as a result of Chlamydia infection (Vanderlasche, 1982).
Although the transmission of Chlamydia from sheep to cattle has not been
proved, it would be wise to separate rams (and ewes) from bulls at an AI centre.
