Chlamydial infection in animals

Other Vertebrates

Chlamydial or Chlamydiae-like infections occur in an enormously diverse range of animal species, from the humble Amoeba and Hydra through arthropods, insects, molluscs, marsupials, birds, reptiles and mammals to humans. Arguably this is the widest host species range of any group of microorganisms. However, adequate identification of the apparent Chlamydiales associated with these infections is often lacking.

Mammals

Among mammals, chlamydiae have been isolated from rabbits, ferrets and opossums Storz, 1988. In rabbits chlamydiae cause spontaneous abortion Parker et al., 1966 and pneumonia Storz, 1988. Many strains and colonies of mice are inapparently infected with chlamydial agents Karr, 1943. Isolates were recovered from the lungs of clinically normal mice. Chlamydial strains have also been isolated from seemingly healthy wild rodents Eddie et al., 1969. These respiratory isolates were probably strains of Chlamydia muridarum, formerly classed as the mouse biovar of C. trachomatis.

There are a number of reports of chlamydial infections in buffaloes. Gupta et al. 1976 described pneumonia in a buffalo calf, while Dhingra et al. 1980 isolated chlamydiae from the lungs of buffaloes with pneumonia. Rowe et al. 1978 recovered a Chlamydia psittaci-like agent from wild African buffalo. More recently, chlamydial was diagnosed in water buffalo calves in southern Italy. Infected animals were affected with recumbency, depression and limb paralysis, but fever was not observed. A chlamydial isolate from a calf was shown to be C. pecorum by ompA PCR and by sequencing the 16S-23S intergenic spacer region Magnino et al., 2000a. C. pecorum was also recovered from the lungs of a wild chamois in the Italian Alps which had pneumonia Magnino et al., 2000b.

Serological surveys suggest that chlamydial infections occur in a large range of mammals including monkeys, wild boar and hedgehogs Storz, 1988; deer in the USA Debbie, 1967; Taylor, 1996 and Italy Giovannini et al., 1988 and reindeer in Lapland Neuvonen, 1976. Four species of wild ruminants from a nature reserve in Spain, (fallow deer, mouflon, red deer and Spanish ibex), were infected with chlamydiae. These species apparently acted as reservoirs of chlamydial infection; transmission between wild and domestic ruminants (sheep and goats) occurred through grazing on the same pastures Cubero-Pablo et al., 2000. An epizootic of infectious keratoconjunctivitis occurred in free-ranging mule deer in Utah, and chlamydiae, as well as other organisms, were isolated Taylor, 1996. An examination of sera from reindeer in Lapland, Finland, revealed antibodies to chlamydia. In another study, serological evidence of chlamydial infection was also reported in antelope Mansell et al., 1995 and in captive Arabian oryx from various countries Greth et al. , 1992. Chlamydiae were isolated from fur seals in the Canadian Arctic by Eddie et al., 1966 while systemic infection with chlamydiae led to major mortalities in snowshoe hares and muskrats in Saskatchewan, Canada Spalatin et al., 1965.

Birds

More than 200 species of bird are known to be infected by chlamydiae [see C. psittaci Introduction].

Reptiles

There are a number of reports of chlamydial infection and disease in reptiles. In an examination of different chameleon species from Tanzania, one lizard became ill and Chlamydia-like organisms were demonstrated in inclusions in macrophages from the spleen and liver Jacobson and Telford, 1990. Chlamydiae were responsible for moderate levels of death among farmed green sea turtles in the Cayman Islands Homer et al., 1994. Clinical signs included lethargy, anorexia and an inability to dive. Post-mortem study showed necrotising myocarditis, as well as pneumonia, and chronic or active enteritis . A disease syndrome in farmed, hatchling Nile crocodiles, consisting of acute hepatitis and oedema, is caused by C. psittaci Huchzermeyer et al., 1994. Chlamydial infection is also a major disease problem on crocodile farms in Zimbabwe. Fortunately these infections respond to oxytetracycline treatment. Cold-blooded vertebrates might represent a source of chlamydial infection for warm-blooded hosts. Subsequently, Huchzermeyer, 1997 indicated a potential risk to human health arising from crocodile and possibly ostrich meat. Although chlamydial infections are common on some crocodile farms in southern Africa, there is little evidence of chlamydial infection in ostriches.

Amphibians

PCR studies indicate that a pneumonia and anaemia disease syndrome in wild giant barred frogs in Australia is probably caused by the Koala biovar of Chlamydophila pneumoniae. This was thought by the authors to be the first report of a chlamydial strain infecting both warm and cold blooded host. The giant barred frog has the distinction of being the fourth known host for C. pneumoniae, in addition to humans, koalas and horses. Chlamydial infections have also been described in another amphibian species, the African clawed frog Newcomer et al., 1982. A chlamydial isolate was recovered from animals dying of spontaneous disease, and was used to reproduce the disease on inoculation into other frogs. A similar lethal outbreak was described by Howerth, 1984. Infected frogs had liver lesions, degeneration and inflammation of kidneys, myocarditis and necrosis of the spleen. Reed et al., 2000 isolated C. pneumoniae from African clawed frogs among whom an epizootic of chlamydiosis had caused death in 90% of the breeding colony.

Fish

The agent causing epitheliocystis disease of the gills in fish is considered to be chlamydia or a chlamydia-like organism. Wolke et al., 1970 found chlamydial infection causing chronic gill disease in Connecticut striped bass and white perch. Moribund opaleye fish were also shown to be infected with chlamydia spp., although other pathogens were present Kent et al., 1988. Chlamydial infection caused epitheliocystis disease in cultured pacu, a tropical fish species in Brazil, leading to heavy mortality Szakolczai et al., 1999. Epitheliocystis was also detected in sea bream by Crespo et al., 1999. Electron microscopy findings suggested that the infection in sea bream may have been caused by a unique, pleomorphic, and unknown Chlamydia-like agent.

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