Chlamydophila Felis.pdf

Chlamydophila Felis of Gram-negative bacteria, and their DNA is also contained within nucleoids that are not Introduction separated Chlamydophila felis (...

Chlamydophila Felis of Gram-negative bacteria, and their DNA is also contained within nucleoids that are not Introduction separated Chlamydophila felis (previously feline from the cytoplasm by a membrane. The Chlamydia psittaci) was first isolated in genome hens’ eggs in the USA from cats with sizes of Chlamydia psittaci and respiratory disease in 1942 (Baker, Chlamydia trachomatis 1942). Because C. felis was the first have been estimated to be around 1450 feline respiratory pathogen to be kb (Frutos identified, it was initially believed that et al., 1989). most cases of feline upper respiratory Chlamydiae are placed within the order tract disease (URTD) were the result of Chlamydiales chlamydial infection.With the isolation and family Chlamydiaceae. Until of feline calicivirus (FCV) and feline recently, herpesvirus-1 (FHV-1) in the late 1950s, a single genus, Chlamydia, was the importance of C. felis was recognised, containing questioned. In the late 1970s, however, the four species C. trachomatis, C. a number of studies re-emphasised its psittaci, C. pneumoniae importance as a conjunctival pathogen and C. pecorum. However, results of 23S of cats. There is some evidence rRNA gene analysis have shown that that C. felis may occasionally be chlamydiae can associated with other clinical signs, be divided into nine groups, which such as vaginal discharge, although correlate with the much remains to be learned about the host species infected. Therefore, importance of these conditions. Chlamydiae have now been reclassified into nine species Aetiology belonging to Chlamydiae are obligately intracellular two genera, Chlamydia and Gram-negative Chlamydophila (Everett bacteria. Unlike viruses, they possess et al., 1999). The genus Chlamydia both DNA and includes Chlamydia RNA, their replication cycle involves trachomatis, infecting humans, binary fission Chlamydia muridarum, and they are susceptible to certain infecting rodents, and Chlamydia suis, antimicrobial infecting drugs. Unlike Rickettsiae, they lack a swine. Chlamydophila comprises cytochrome Chlamydophila system for electron transport and pecorum (previously Chlamydia cannot synthesise pecorum), which adenosine triphosphate (ATP) and infects cattle and sheep, Chlamydophila guanosine triphosphate pneumoniae (GTP). Their cell walls show similarity to (previously Chlamydia pneumoniae), as those well as four new species derived from Chlamydia psittaci: 1960; Kuroda-Kitogawa et al., 1993). Chlamydophila Randomamplification of polymorphic psittaci, Chlamydophila abortus, DNA fingerprinting Chlamydophila has demonstrated the existence of at caviae and Chlamydophila felis, which least two feline generally infect strains (Pudjiatmoko et al., 1997). birds, sheep, guinea-pigs and cats, Although the respectively. major site of antigenic variation in C. Chlamydia trachomatis is a well- trachomatis is characterised in the major outer membrane protein species. In humans, certain serovars of gene (ompA), C. trachomatis DNA analysis has shown that ompA is are responsible for a chronic highly conserved keratoconjunctivitis between different C. felis isolates known as trachoma, a major public (Sayada et al., health problem in 1994;May et al., 1996; Sykes, 1997). developing regions such as North Africa The chlamydial developmental cycle and southeast involves an Asia (Stamm, 1998). Other serovars alternation between the predominantly cause mainly extracellular, ocular, genital, or both ocular and genital infectious elementary body (EB), infections measuring 0.3_m in humans, which are spread mainly by in diameter, and the intracellular, sexual transmission metabolically active with occasional ocular transfer. reticulate body (RB), measuring 0.5– Chlamydia 1.5_m in diameter. pneumoniae is a major cause of Only the RB can divide, which occurs in pneumonia in an intracellular humans, and has also been associated vacuole called an inclusion. The length with acute to of the chronic bronchitis, sinusitis, pharyngitis, cycle in cell culture varies from 48 to 72 coronary h. The RBs artery disease, asthma, cerebrovascular then reorganise into EBs, which are disease, subsequently sarcoidosis and reactive arthritis. released from the host cell and may Chlamydophilia enter a new, uninfected psittaci and C. abortus are zoonoses, host cell, where they reorganise into causing respiratory RBs. and reproductive disease, respectively. Chlamydial EBs survive for only a few Serological studies suggest that days at room multiple strains of temperature. Survival for up to 1 month C. felis exist, which may differ in at 4°C may virulence (Yerasimides, be possible (Baker, 1942). They are inactivated by lipid solvents and detergents, but are Persistent chlamydiae in the form of somewhat atypical RBs resistant to acids and alkalis. have been identified in the joints of humans with Pathogenesis reactive arthritis. Localisation of Much remains unknown regarding the persistent Chlamydiae pathogenesis to deeper tissues, such as the of chlamydial infections in cats. The subsynovial layer in organism patients with arthritis (Beutler et al., appears to have a predilection for the 1995),may afford conjunctival protection from the continual rapid cell epithelial cell. Natural transmission of C. turnover felis, as for characteristic of epithelial tissues. the other respiratory pathogens, Chlamydophilia felis may also be presumably occurs capable of entering by close contact with other infected cats a persistent state within tissues. and their Conjunctivitis aerosols, and via fomites. Mutual associated with C. felis may persist for grooming and selfgrooming several months. are probably important means of natural Organisms have been isolated from the inoculation. It is unclear whether natural conjunctiva transmission for up to 215 days after experimental by the venereal route occurs in cats. The infection, incubation although most cats cease conjunctival period in experimentally infected cats is shedding at approximately 3–5 days. around 60 days after infection (Wills, Infections caused by chlamydiae tend to 1986; O’Dair follow a et al., 1994). Persistent elevations in chronic, insidious course, often serum titres to C. progressing through felis, despite apparent cessation of asymptomatic stages. chlamydiae may shedding, also suggest be capable of that some cats may be capable of passing through periods of delayed harbouring development interspersed persistent chlamydiae. The intestinal with production of new crops of tract may be infectious EBs. a site of persistent infection in cats, as Human chlamydial infections of up to 20 has been years’ duration shown in birds and ruminants. have been reported in the literature. It is Prolonged rectal and unclear vaginal excretion by cats with whether chronic disease is the result of experimentally induced repeated reinfection chlamydial conjunctivitis has been or the presence of persistent documented chlamydiae. (Wills, 1986). The occasional finding of the healthy conjunctival sac, can also C. felis in the act as secondary spleen, liver and peritoneum of cats has invaders and worsen disease. not been consistent, and the significance of the presence of Clinical signs organisms Respiratory and ocular disease in these locations remains unclear Since the discovery of C. felis, there has (Baker, 1944; been much Dickie & Sniff, 1980; Hoover, 1980). controversy regarding the extent of Chlamydial disease may be exacerbated disease attributable by superinfection to the organism. Chlamydophilia felis is with other microorganisms. In one primarily a conjunctival pathogen, study, 8% capable of causing acute to of cats had both chlamydial and either chronic conjunctivitis, with FCV or FHV-1 blepharospasm, chemosis infection (Wills et al., 1988a). Cats with and congestion and a serous to concurrent mucopurulent ocular FCV infection had additional signs, such discharge, but no dyspnoea or coughing as oral ulceration, (Plates 27.1 in addition to conjunctivitis. Dual and 27.2). Mild pulmonary lesions may infection result from with FCV appears to be more common aerosol exposure (Hoover et al., 1978), than with but as these are FHV-1, although this may relate to the clinically insignificant, C. felis is no ease of detection longer known as the of FCV compared with FHV- ‘feline pneumonitis agent’. Transient 1.Coinfections with pyrexia, reduced feline immunodeficiency virus (FIV) appetite and weight loss may occur prolong the shortly after infection, duration of conjunctivitis and chlamydial although many cats remain well and shedding continue to and, in cats with existing FIV infection, eat. An acute-phase reactant response superinfection was shown to with C. felis may accelerate the clinical accompany pyrexia in experimentally progression of infected cats FIV infection (O’Dair et al., 1994). Both (TerWee et al., 1998). Clinical signs Mycoplasma improve after a few species and Bordetella bronchiseptica weeks, but mild conjunctivitis frequently can complicate persists for C. felis infections (Shewen et al., 1980; several months. Nasal discharge and Sykes, 1997). sneezing may Other bacteria, including those that occur in some cats. The strain and/or normally colonise the route of infection may influence the extent of respiratory antibody (MDA; see below) (Plate tract 27.3).Whether or involvement. Sneezing and nasal not such cases are associated with discharge without genital infection concurrent ocular involvement is highly in the queen, as occurs in humans unlikely to be infected with associated with C. felis infection (Sykes C. trachomatis, is unclear. et al., 1999b). In contrast to ocular chlamydial Reproductive tract disease infections of other Causal relationships between host species, C. felis infection is rarely chlamydial infections associated with and reproductive disease have been corneal damage. Reported cases of recognised in corneal involvement, many host species. Chlamydophilia felis including punctate keratitis and scarring, has been suspected did as a cause of abortion, neonatal not exclude the possibility that corneal mortality and disease was infertility in catteries, but a definite attributable to dual infection with other causative link has pathogens, not been reported. Infertility and such as FHV-1 (El-Sheikh, 1978; abortion have been Tabatabayi & Rad, equally distributed between infected and 1981). One study showed that uninfected simultaneous inoculation colonies (Pointon et al., 1991) and many of a Streptococcus species isolate with chlamydiainfected C. felis was colonies do not have reproductive more likely to be associated with problems. keratoconjunctivitis. FHV-1 may be responsible for a number Corneal ulceration occurred in half of of suspected the cats cases of C. felis-induced genital and infected (Darougar et al., 1977). The perinatal disease. ability of the FHV-1 was detected in four of eight cats organism to cause corneal disease may with combined also be reproductive and URTD in a large dependent on strain and/or host factors. epidemiological Chlamydophilia felis has occasionally survey of cats with URTD, whereas C. been isolated felis from cases of neonatal conjunctivitis in was not detected (Sykes et al., 1999b). kittens In experimentally infected cats, isolation (Sykes, 1997; Wills & Gaskell, 1994), of although most chlamydiae from the vagina has been kittens appear to be protected by associated with a maternally derived vaginal discharge (Wills, 1986; O’Dair et al., 1994; Sykes et al., 1999a). Intravaginal and by blood transfusion (TerWee et al., intraurethral 1998). inoculation has been associated with Systemic signs and conjunctivitis vaginal discharge, developed 7 and 35 bleeding and swelling in females; days later, respectively. Failure to detect urethritis C. felis in the and urethral discharge in males, and blood using PCR may reflect the proctitis in both presence of extremely sexes (Darougar et al., 1977; El-Sheikh, low numbers of organisms in the blood, 1978). Other or a very investigators have been less successful short period of chlamydaemia that was in their attempts undetected. to isolate chlamydia from the rectum or Infection of placental tissues using PCR vagina. One has been report suggested that vaginal shedding demonstrated in a cat experimentally of chlamydia infected with may be affected by the age of the cat, C. felis during gestation (Sykes, 1997). with kittens less Placentitis was than 13 weeks of age failing to shed not observed histologically and no organisms from evidence of infection the vagina (TerWee et al., 1998). Direct was detected in the neonates. The inoculation of queen experienced C. felis into the oviducts led to apparently normal parturition, but salpingitis and growth vaginal of the organism in this location for shedding of C. felis began immediately weeks, with minimal afterwards systemic signs (Kane et al., 1985). and continued for at least 12 days. This Although the is similar to valvular structures in the feline observations in ewes following abortion reproductive tract or birth of may prevent chlamydial infection weak lambs. It is possible that C. felis ascending from the infection may be vagina, haematogenous dissemination influenced by the host’s endocrine may allow the environment, as agent to relocate to the reproductive has been shown for other host species. tract. Although C. felis DNA could not be detected using criteria may need to be met. In other the polymerase species, the ability chain reaction (PCR) in serial blood of Chlamydiae to cause reproductive samples disease can collected from experimentally infected depend on the stage of pregnancy at cats (Sykes which infection et al., 1999a), infection has been occurs, coinfection with other transmitted experimentally organisms, concurrent immunosuppression, route of infection inoculum. Transient lameness was also and the strain noted in one involved. of the author’s experimentally infected Other manifestations cats. Further Chlamydial infection has been studies are required to determine associated with peritonitis whether lameness in a mature female cat (Dickie & Sniff, may be associated with C. felis infection 1980). in the field Squamous cells and macrophages in situation, and whether the lameness the peritoneal reflects predominantly exudate and intestine contained immune-mediated phenomena, as chlamydial inclusions, occurs in although the authors were unable to humans with Reiter’s syndrome, or transmit direct damage the infection to kittens. Peracute illness resulting from intrasynovial chlamydial and death replication. associated with systemic chlamydiosis Epidemiology has been The prevalence of C. felis infection has reported in a fishing cat housed at a been examined zoological park using a variety of different assays in in The Netherlands (Kik et al., 1997). several different Chlamydiae were observed in the gastric geographical locations. Using the mucosa of complement 12 young cats from five related research fixation test (CFT), the prevalence of or commercial anti-chlamydial breeding colonies (Hargis et al., 1983). antibodies in cats has ranged from 0 to Four of 32%. Serological the cats showed signs of weight loss of studies in the USA and from 1991 undetermined onwards in the UK cause. Administration of the organism are confounded by the effects of to cats by vaccination. Also, aerosol and oral inoculation resulted in recent infection with C. felis correlates conjunctivitis, poorly with rhinitis and, in some, mild gastritis. the presence of CFT antibodies. The Recently, an association between prevalence of C. chlamydial infection felis in cats with URTD as determined and lameness in cats has been reported using culture (TerWee has ranged from 23 to 31% (Wills et al., et al., 1997, 1998). Lameness occurred 2 1988a; weeks after Hanselaer et al., 1989). The author the onset of conjunctivitis in 10 of 19 recently used PCR experimentally on conjunctival swabs to obtain a infected cats, and only in cats receiving prevalence of a high dose of 66/462 (14.3%) in cats with URTD episode of URTD, which included (Sykes et al., conjunctivitis, 1999b). 2 months previously. Studies using both culture (Wills et al., Zoonotic potential 1988a) and Another area of controversy surrounding PCR (Sykes et al., 1999b) have shown feline that cats in the chlamydiosis is its zoonotic potential. 2–6 month age group are most likely to Chlamydophilia be infected felis has been implicated in with C. felis. In the author’s study, the conjunctivitis in humans, prevalence was but evidence to support this association also high in cats aged 7–11 months. has not been The next most strong. One report involved a man with frequently affected group was cats less unilateral follicular than 8 weeks of conjunctivitis. His 12-week-old kitten, age. However, in another study, cats 5 which weeks of age or slept on his bed, also had a unilateral younger were relatively protected from ocular discharge chlamydial (Ostler et al., 1969; Schachter et al., infection, presumably owing to passive 1969). The man immunity lived in a crowded boarding house with (Wills et al., 1988a). Cats older than 5 several other years of age humans, cats, dogs and monkeys. were least likely to be infected with C. Chlamydiae were felis. There does isolated from the kitten and the affected not appear to be a strong predilection human, and for any particular distinguished from C. trachomatis by breed or sex. their failure to The prevalence of C. felis in uptake iodine. Most recently, a non- asymptomatic cats is trachomatis low. None of 50 cats was positive using chlamydia was isolated from a human culture immunodeficiency (Shewen et al., 1980) and one of 95 cats virus (HIV)-positive man with chronic was positive conjunctivitis, using PCR (Sykes et al., 1999b). who had recently acquired a stray queen Persistent chlamydial and its kittens. A chlamydia was shedding after resolution of clinical subsequently isolated signs may explain from one of the kittens, which was positive results in some asymptomatic shown to be identical cats (see to that isolated from the man, using Pathogenesis, above). The one restriction digestion and partial asymptomatic cat that sequencing of the omp2 gene was positive using PCR had recovered (Hartley et al., 2001). The omp2 gene from an sequence matched that of C. felis.However, only four of 21 which is now known to be caused by the owners of cats Gramnegative with chlamydial conjunctivitis bacteria Bartonella henselae and B. complained of recent clarridgeiae. itchy or sore eyes, compared with two of These implications were made primarily eight owners on the basis of cats that were negative for C. felis of serology. Recent studies have (Wills, 1986). described serological Chlamydophilia felis has also been cross-reactions between Bartonella and incriminated as a Chlamydia cause of other disease in humans, species (Maurin et al., 1997), and these including hepatosplenomegaly, may be glomerulonephitis and endocarditis responsible for the erroneous (Griffiths et al., 1978; Regan et al., 1979). interpretations of However, in Chlamydia in CSD. all these cases, associations were made Diagnosis on the basis of Chlamydial infection needs to be serology, which is not species specific. differentiated from It is possible other infectious and non-infectious that the pathogen involved in some or all causes of feline of these cases URTD. It is not possible to differentiate was the more recently discovered C. infections pneumoniae, caused by the three major respiratory which also fails to stain with iodine. If C. pathogens on felis is the basis of clinical signs and, because zoonotic, maintenance of hygienic mixed infections conditions and may also occur, accurate diagnosis prompt treatment of affected cats is requires recommended to some form of microbiological assay. prevent human disease, although further Examination of Giemsa-stained investigation conjunctival smears of the zoonotic potential of this for chlamydial inclusions is not currently organism is needed. recommended Adherence to guidelines for people with as a reliable means of diagnosis of immunodeficiencies feline to reduce public health risk of their pets chlamydial infection. Inclusions are should also minimise the risk of generally only infection by C. felis visible early in the course of infection, (Greene, 1998a). and sometimes Chlamydia has also been implicated in not at all (Wills, 1986). False positives cat scratch may occur as disease (CSD) in humans (Emmons et a result of confusion with melanin al., 1976), granules in the cytoplasm of conjunctival cells. Serum antibody titres detected using 27.4). This is more sensitive than direct indirect application of immunofluorescence correlate well with fluorescent antibody to smears of recent infection. affected tissues. Ninety-six per cent of cats infected with Special transport media containing C. felis appropriate antimicrobials have titres _32, compared with only 7.5% are required to preserve chlamydial of uninfected viability. cats (Wills et al., 1988a). Unfortunately, Isolation in cell culture is technically a diagnosis demanding, is often required before there is an time consuming and expensive. appreciable Transportation and rise in antibody titre. The CFT is storage problems can affect the unreliable in detecting sensitivity of cell culture, recent C. felis infection (Cello, 1971). and some samples may be toxic for cell Various enzyme-linked immunosorbent culture assay monolayers. The sensitivity of culture (ELISA) antigen kits are available for the may vary from diagnosis of laboratory to laboratory depending on human C. trachomatis infection, which equipment and have variable technical expertise. sensitivities and specificities for Diagnostic PCR assays are now used detecting C. felis. For routinely for example, one assay was found to have a diagnosis of human chlamydial specificity infections, and assays of 90% and a sensitivity of 79% for C. felis are becoming increasingly compared with cell available. PCR culture (Wills et al., 1988b), whereas has been shown to have good sensitivity another had a and specificity sensitivity of 25% and specificity of 84% with proper sample collection and compared storage with direct fluorescent antibody (McDonald et al., 1998; Sykes et al., (Pointon et al., 1991). 1999a). Nucleic These assays may be of some benefit acid amplification techniques are more where other, rapid, less more sensitive assays are not available. expensive and in many cases more The gold standard for chlamydial sensitive than traditional diagnosis is cell techniques such as culture and ELISA. culture, which most commonly uses Use of fluorescent antibodies a real-time PCR assay to detect C. felis to detect intracytoplasmic chlamydial has also been inclusions reported, which is capable of quantifying following inoculation of cell monolayers the number (Plate of organisms within a clinical sample down to 10 genomic copies (Helps et al., 2001). The biggest problem with all nucleic acid amplification techniques is false positives resulting from contamination, which may occur before sample submission or after submission to the laboratory. Veterinarians collecting samples for PCR should contact the laboratory for sample