Bacteria Genomes - CHLAMYDOPHILA ABORTUS

Chlamydophila abortus is a Gram-negative intracellular bacterium that was formerly known as Chlamydia psittaci immunotype 1

Chlamydophila abortus is a cause of abortion and foetal loss in sheep, cattle and goats. Infection with strains of this microorganism has also been associated with abortion and other clinical symptoms in humans. Abortion isolates from sheep have produced abortion and mastitis in cattle, and pneumonia in pigeons, turkeys and sparrows. In addition, chlamydial isolates excreted in sheep and cattle faeces have also caused abortion in both of those ruminant species

C. abortus strains are endemic among ruminants and efficiently colonize the placenta. They have a distinctive serotype and nearly 100% conservation of ribosomal and ompA sequences. C. abortus is the reference strain for determining whether a new strain belongs to the Chlamydiaceae (16S- or 23S-rRNA should be > 90% identical to the C. abortus genes).

The first report of enzootic abortion in sheep was in Scotland in 1936. The aetiological agent was identified later (1950). Subsequently, chlamydial abortion in sheep, [also known as ovine enzootic abortion (OEA) or enzootic abortion of ewes (EAE)], has been recognised as one of the most important causes of abortion in sheep. Chlamydial abortion in late pregnancy causes serious reproductive wastage in many sheep-rearing areas of the world, particularly where flocks are closely congregated during the parturient period. Infected animals show no clinical illness prior to abortion. Pathogenesis commences around day 90 of gestation coincident with a phase of rapid fetal growth when chlamydial invasion of placentomes produces a progressively diffuse inflammatory response, thrombotic vasculitis and tissue necrosis. Milder changes occur in the fetal liver and lung and, in cases in which placental damage is severe, there may be evidence of hypoxic brain damage. Abortion probably results from a combination of impairment of materno-fetal nutrient and gaseous exchange, disruption of hormonal regulation of pregnancy and induced cytokine aggression. Infected females shed vast numbers of infective C. abortus at the time of abortion or parturition, particularly in the placenta and uterine discharges.

In the U.K., chlamydial abortion in sheep was successfully controlled in the 1960s and 1970s by the use of a single C. abortus strain, formalin-inactivated, egg grown vaccine. This induced an immunity lasting about 3 years but did not offer complete protection. Disease started to reappear in vaccinated flocks in S.E Scotland in the late 1970s and spread to other areas of the country and has continued to increase each year. In 1995, about 1600 flock incidents of chlamydial abortion in ewes were diagnosed in England, Scotland and Wales. It has been speculated that more virulent strains of C. abortus have emerged since the 1970s causing a breakdown in vaccine protection.

References:

http://www.chlamydiae.com/docs/Chlamydiales/genus_chlamydophila.asp
http://www.cdc.gov/ncidod/EID/vol9no12/02-0566.htm
http://www.chlamydiae.com/restricted/docs/infections/vet_cabortus_intro.asp
http://www.oie.int/eng/normes/mmanual/A_00073.htm
http://www.sanger.ac.uk/Projects/C_abortus/