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This article was published in 1975
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Chlamydial Diseases - Including Chlamydial Arthritis of Lambs
R.I. Walker, B.V.Sc., Veterinary Inspector, Young.
INTRODUCTION
The organisms or agents broadly grouped together into the Psittaxois-Lymphogranuloma-Venereum-Trachoma or P.L.V. disease group which, for some time, were thought to be 'viral' in structure are now considered to be bacteria, belonging to a single genus, Chlamydia.
The diseases caused by this P.L.V. group are quite numerous and indeed some are quite serious in their own right and although (sic) Chlamydia (C. ovis) we could spend a little time with some of these other diseases before dealing more specifically with one member.
RELATIONSHIPS
It may be beneficial firstly to place the Chlamydia in perspective as far as their classification is concerned and to consider their relations in this classification. The family Chlamydiaceae is one of four within the Order Rickettsiales, the others being: -
1. The Rickettsiaceae containing those agents responsible for Typhus (man), Rocky Mountain Spotted Fever (man), Q Fever (man) and 'Heartwater' (Cattle, sheep and goats) to name a few, and all of which with the exception of Q Fever have arthropods as natural hosts and which transmit the disease to incidental mammalian hosts.
2. the Bartonellaceae is made up of those agents which parasitise erythrocytes of man and lower animals and includes diseases such as Bartonellosis (man), Haemobartonellosis (various animals) and Eperythrozoonosis (sheep).
3. the Anaplasmataceae - a single genus of organisms causing Anaplasmosis in ruminants, a parasitic disease of erythrocytes creating anaemia and icterus and variable mortality.
For a long while these organisms were regarded as Protozoa and placed with the Babesia organisms in the same class, however academic identification has since separated Anaplasma agents from the Protozoa.
FAMILY CHLAMYDIACEAE
Structure
The single genus of Chlamydial agents are related by a common morphology, development cycle and group antigen.
They are generally spherical, intracytoplasmic parasites ranging in size from 200 mµ - 1000 mµ and when they enter a host cell an intracytoplasmic inclusion is formed ranging in size up to 12 µ diameter.
They contain both nucleic acids, D.N.A. and R.N.A., have cell walls similar to Gram negative bacteria, although they only stain weakly Gram negative and show some susceptibility to antibiotics, generally those of the tetracycline group. The group stain readily by Giemsa (purple), Castenada (blue) and Macchiavellos' method (red) and are clearly visible in the cytoplasm of host cells under phase contrast microscopy.
There are thirteen species. Classified within the Chlamydia group according to the disease they produce and the antigenic specificity of a particular lipoprotein component.
All members of the group have a group specific antigen and some evidence exists that the species specific antigen is also present.
CHLAMYDIAL DISEASE IN MAN
The chlamydial infections in man can be subdivided into two groups based on the mode of transmission. Direct person to person transmission occurs in Trachoma, inclusion conjunctivitis and Lymphogranuloma venereum. In the second group, a heterologous infectious chain involving birds, domestic animals and man may lead to respiratory infections in man as an accidental host.
AVIAN CHLAMYDIOSIS
Chlamydiosis has been the name accepted to replace Psittacosis and Ornithosis which were previously used to define the disease in man or psittacine birds and in non-psittacine birds respectively.
The latent, inapparent chlamydial infection has long been recognised as the predominant and most important state in the relationship between chlamydial agents and birds. However, overt disease has been encountered in most species of pet birds and domesticated poultry. In all instances the younger birds are more susceptible. Crowding or otherwise unfavourable environmental conditions and stress from shipping, racing and handling contribute to the severity of the disease. This has been most noticeable in the United Kingdom since the release of the ban on importation of psittacine birds in 1966, in both the avian and human fields.
Chlamydiosis (Psittacosis) has generally become an occupational disease in man; in workers in the poultry industry where the disease is one of severe systemic involvement following an initial pneumonitis and causing a 20% mortality in untreated humans.
CHLAMYDIAL DISEASE IN RUMINANTS.
In recent years more economic importance has been placed on chlamydial disease in domestic animals throughout the world. In Australia, however, recognition of the diseases has been somewhat limited, and to date those diseases known to exist here are Sporadic Bovine Encephalomyelitis (SBE) and Polyarthritis in lambs and perhaps a Chlamydial conjunctivitis, while there are suspicions that Enzootic Abortion of Ewes (EAE), intestinal chlamydia in Ruminants and Chlamydia induced pneumonia may be present here also.
POLYARTHRITIS OF LAMBS.
In the U.S.A. this disease is recognised in feedlot lambs and in range conditions and in Australia an identical disease is seen under similar extensive and semi-intensive conditions.
The morbidity rate varies from 2-75% in range and intensive situations respectively. In the U.S.A. workers describe the disease in lambs weighing 55-105 pounds, where these lambs appear affected more than the smaller, younger lambs, but in Australia, quite young lambs have been seen with the same clinical signs.
Clinically rectal temperatures varied from 39-42 degrees, Centigrade and is dependent on the acuteness and stage of the disease. The lambs have a varying degree of stiffness, lameness and anorexia and some may have a conjunctivitis. Joint enlargement is generally not noticeable, but in long-standing, advanced cases, slight enlargement of the stifle, hock and elbow joints can be detected. In the Northern hemisphere the disease appeared to be more common in mid-summer to autumn under range conditions and later under feed lotting, whereas in Australia the highest incidence is probably Spring and Summer, and incidence is more commonly in the range of 2-10%.
It is interesting to note that the strain of Chlamydia producing polyarthritis appears identical (antigenically) to that causing a polyarthritis in calves. However, the disease in lambs has a low mortality rate where-as the condition, particularly in young calves is quite often fatal.
Breed differences in sheep may not be important but it appears that Merino sheep may not be susceptible, as British Breeds, e.g. Dorset and South Suffolk and British breed x Merino crosses are more commonly effected.
Pathological findings are generally of an articular and periarticular nature. There is hyperaemia and oedema of affected joints - stifle, hock, elbow and hip joints - and a greyish-yellow synovial fluid is found. Often grey-yellow flakes and plaques of different sizes and shapes are seen in advanced cases.
The degree of these reactive changes varies with the acuteness and duration of the disease.
Histopathologically, inflammatory and proliferative changes are seen in tissues surrounding joints and infiltration by mononuclear inflammatory cells which contain Chlamydial inclusions are also observed commonly in the early stages.
Soft tissues including spleen and liver in lambs contained intracytoplasmic inclusions in reticular cells and inflammatory infiltration cells in both tissues. Cerebrum, cerebellum, kidneys, heart and lungs may also be affected by less consistent findings of oedema, petechiation and hyperaemia. In calves, similar lesions are found as well as splenic enlargement and swollen lymph nodes.
A systemic infection evidently precedes the infection of joint tissues and a typical polyarthritis can be set up experimentally via oral, s/c, i/m, i/v i/articular routes and in the field it is supposed that the oral route is the immediate source of infection. However, it has also been found that while normal sheep may contain chlamydial agents in faeces, these were antigenically different from those strains found in joint and faecal samples from polyarthritis lambs. Obviously some alteration of antigenicity controls whether or not the organism becomes pathogenic.
Moderate to severe inflammatory changes are recognised on the seventh (7th) day and chlamydia can be isolated from hip, knee, shoulder and elbow joints of lambs at that time. However, cultures of joint fluid are invariably negative 28 days after experimental inoculation.
DIAGNOSIS.
Isolation of the causative organism is the ideal situation for diagnosis, however, this is not readily accomplished. Joint fluid is probably only of value up to 14 days post-injection, while a more reliable diagnosis may be made through the use of citrated blood from an animal very early in the course of the disease.
Smears of synovial fluid or tissues may reveal chlamydial inclusions in synovial lining cells, fibroblasts and endothelial cells, Most mononuclear cells may contain chlamydial inclusions.
More detailed techniques using fluorescein conjugated antibodies could verify the presence of chlamydia and their inclusions.
SEROLOGY
The complement-fixation test is the main blood test. used as an assistance to diagnosis and use is made of the group specific antigen/antibody relationship. However it is only effective in indicating group specific antibodies and is of little value in differentiating infections with antigenically different chlamydial strains.
Maximal titres may be reached within 30 days, depending on the type and intensity of infection and the physiological state of the animal. They may be mediated by use of antibiotics early in the course of the disease. After this period of 30 days the titres decline over a period of months.
Paired sera, where a rise in titre can be demonstrated, is a more useful comparison using the C.F. test. As a guideline however the following table may be of some value where diagnosis is anticipated on single blood samples.
| C.F.T. Titre | Interpretation |
|---|---|
| neg - 10 | Negative |
| 10 - 80 | Doubtful |
| >80 | Positive |
Differential Diagnosis
Lambs with mineral deficiency, e.g. Enzootic Ataxia (copper) calcium and phosphorous, osteomalacia or White Muscle Disease (WMD) usually do not show a febrile reaction as can often be shown in the early stages of chlamydial polyarthritis. Radiologically there is no mal-alignment of bones in polyarthritis as compared to the abnormal osteogenesis in the first two conditions. The distinct muscle lesions in WMD are pathognomonic.
Advanced Erysipelas infection usually causes eburnation with compensatory marginal lipping and osteophyte formation, none of which are found in polyarthritis.
Mycoplasma arthritis could be an entity easily confused and differentiation would depend on isolation of the infective agent.
In the realms of exotic disease a laminitis due to Bluetongue virus would be considered in most areas other than Australia.
Treatment is somewhat debatable. In lambs, the majority appear to recover quite well without any specific therapy, however, as the disease is probably recognised more in stud sheep intramuscular injections with Penicillin/Streptomycin or Tetracyclines, early in the disease appear variably beneficial, but in advanced cases treatment is unrewarding.
Mention should also be made of some other important chlamydial diseases in Ruminants, some of which are present in Australia and some others where the disease is suspected.
Sporadic Bovine Encephalomyelitis (SBE)
With this particular disease widely recognised in many parts of New South Wales it was interesting to read recently that the District Veterinary Officer, Narrabri (Monthly Report, October, 1974) made mention of an incidence of 10% (morbidity) of lambs with Chlamydial arthritis occurring on a Narrabri property where SBE in Cattle has been confirmed in the past and in an area where it is recognised as being endemic. The fact that polyarthritis in lambs and calves (antigenically identical organisms in both animals) a result of generalised infections involving the invasion of synovial tissues, reflects the similarity with SBE or Transmissible Serositis. However it is considered that SBE is a separate entity caused by an antigenically distinct chlamydia.
Enzootic Abortion of Ewes.
Ovine abortion was originally described in Scotland in 1936 and has since been recognised in Germany, France, Eastern Europe, North Africa, Spain and most of the Western United States of America. Significant Chlamydial antibody titres have been recognised in sheep in South Australia although proof of abortions is lacking and one can only assume the group specific CF test may have been reading titres for other chlamydial agents.
The clinical syndrome of EAE is one of abortions in 1-5% of all ewes with possibly a slightly higher rate amongst younger ewes. Abortions usually occur in the last month of gestation, however early abortions at 100 days are not uncommon, and were the disease gains entry in a flock, abortions may reach as high as 30% of the flock. There is no evidence that impaired fertility occurs during subsequent breeding seasons and most ewes recover uneventfully.
The Chlamydial agents causing EAE are again antigenically different from those causing polyarthritis. This is surprising as in the U.S.A. both diseases have occurred on the one property or in other cases EAE has followed Poly-arthritis on the same farm in following seasons.
A placentitis in ewes is the predominant change in EAE and cotyledons are recognisably necrotic although only a small number may be affected. The placenta may have a thickened, opaque, yellow-pink colour and may be covered with a layer of flaky, clay-coloured exudate.
Lambs aborted near term have a rather clean appearance, but may sometimes be covered with a clay coloured material. Numerous petechiae may be seen after skinning of the legs, hip, head and neck and may also be seen in the thymus, salivary glands and occasionally in lymph nodes. A small number of lambs may have pinpoint, whitish foci on visceral and cut surfaces of the liver. Histologically necrotic foci, composed of eosinophilic reticular cells and necrobiotic neutrophils have been consistently observed in the red pulp of the spleen.
An antigenically identical chlamydia has been found to cause abortions in cattle, recognised in America, Germany, Spain and France as Epizootic Bovine Abortion. Features of this disease are quite similar to those in sheep, with only minor differences. Aborted calves (7-9 months gestation) show a marked ascites and, hepatopathy recognised as a swollen, reddish-yellow coloured and mottled liver.
Conjunctivitis - A contagious Keratoconjunctivitis of sheep has been found to be caused by a Chlamydia in U.K. and U.S.A., and is quite often related to bouts of polyarthritis at the same time, while the agent causing the condition known as 'pink-eye', in Australia, has been called Rickettsia conjunctivae one wonders whether or not this may in fact be the same disease syndrome.
Workers in the U.S.A, recently found Chlamydial conjunctivitis bilaterally in 80% of feedlots (containing 800 - 2,000 lambs 8-10 months old). Chlamydial inclusions and Chlamydia were isolated from 42% of affected lambs. Some lambs also had a concurrent polyarthritis. They raised the question that conjunctivitis could well be the harbinger of polyarthritis, but this may be a situation seen only under such intensive situations. In Australia it may well be that lambs show both conditions in varying proportions and in different seasons.
Other Chlamydia Induced Diseases.
Diseases that we may or may not suspect in Australia have been seen overseas and have Chlamydial organisms identified with them.
A Chlamydia-induced Pneumonia has been recognised in sheep, cattle, pigs, goats, horses and man in various parts of the world. A Chlamydial pneumonia of mice has been recognised in Australia.
While no natural cases of mastitis have been found, experimenters have successfully induced mastitis in cows and ewes and it is supposed that a mastitis could occur naturally following generalised infection with Chlamydial agents.
REFERENCES
Campbell, R.S.F. (1972) Chlamydia Proceedings 16 - Virology and Virus Diseases (p.142-144)
Blood and Henderson. Bailliere Tindall and Coc (1961) First reprint
Diseases of Poultry. Biest on and Schwarte (1965) 5th edition, Dept. of Health - Pt. 4
Storz, J. Chlamydia and Chlamydia-Induced Diseases (1972). C.C. Thomas, Illinois
Hopkins et. al, (1973). J.A.V.M.A. - 163:1157
J. Storz (1966). J.Comp.Path - 76:357-362
J.Storz et. al. (1966). American Journal of Veterinary Research - 27:633 and 987
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Dane and Clapp (1956). Aust. Vet. J. - 32:91-93
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