Vol. 23, No. 3 March 2001 231 CE Article #2 (1.5 contact hours) Refereed Peer Review FOCAL POINT Although Chlamydophila felis infection is an important cause of feline conjunctivitis, much remains unknown regarding its pathogenesis, spectrum of clinical manifestations, and zoonotic potential. KEY FACTS Chronic chlamydial infections may result from the ability of the organism to persist within tissue for prolonged periods, despite the host s immune response, p. 232. The role of C. felis in reproductive disease and as a zoonosis remains unclear, p. 233. Diagnosis is most reliably made using cell culture or the polymerase chain reaction assay, p. 234. Completely eradicating the organism may be possible when all cats in the household are treated with oral doxycycline (5 mg/kg every 12 hours for 3 weeks), p. 234. Chlamydial vaccines have been associated with atypical reactions 7 to 21 days after vaccination in approximately 3% of cats, p. 235. Feline Upper Respiratory Tract Pathogens: Chlamydophila felis * University of Minnesota Jane E. Sykes, BVSc (Hons), PhD ABSTRACT: Chlamydophila felis (previously Chlamydia psittaci var. felis) is a common cause of acute and chronic conjunctivitis in cats. However, knowledge of the pathogenesis of feline chlamydiosis is incomplete, and the involvement of C. felis in reproductive tract disease and its zoonotic potential are controversial. Molecular assays (e.g., polymerase chain reaction) are now routinely used to diagnose human chlamydiosis and are becoming increasingly available for diagnosing chlamydial infections in cats. This article reviews the current knowledge of the pathogenesis, epidemiology, clinical manifestations, diagnosis, and treatment of feline chlamydiosis. Vaccination, immunity, and the public health significance of the organism are also discussed. Chlamydophila felis (previously feline Chlamydia psittaci ) was first isolated in the United States from cats with respiratory disease in 1942. 1 The causative organism was initially thought to be a virus, and the organism and its disease were named feline pneumonitis. 2 Because C. felis was the first feline respiratory pathogen to be identified, most cases of feline upper respiratory tract disease (URTD) were initially believed to result from chlamydial infection. When feline calicivirus (FCV) and herpesvirus-1 (FHV1) were isolated in the late 1950s, the importance of C. felis was questioned. In the late 1970s, however, several studies reemphasized its importance, primarily as a conjunctival pathogen of cats. Because pneumonia caused by the organism is generally subclinical, the term feline pneumonitis is no longer considered appropriate. There is some evidence that C. felis may occasionally be associated with disease of other organs (e.g., the genital tract), but much remains to be learned about the significance of these conditions. CAUSE Chlamydiae are obligately intracellular gram-negative bacteria. Their developmental cycle involves an alternation between a predominantly extracellular infectious elementary body (EB) and an intracellular metabolically active reticulate body (RB). Only the RB can divide, which occurs in an intracellular vacuole *A companion article entitled Feline Upper Respiratory Tract Pathogens: Herpesvirus-1 and Calicivirus appeared in the February 2001 (Vol. 23, No. 2) issue of Compendium.
232 Small Animal/Exotics Compendium March 2001 called an inclusion. The RBs then reorganize into EBs, which are subsequently released from the host cell and may enter a new, uninfected host cell where they reorganize into RBs. Chlamydiae have recently been reclassified into nine species belonging to two genera, Chlamydia and Chlamydophila, based on ribosomal gene sequences. 3 The four new species derived from Chlamydia psittaci (i.e., C. felis, Chlamydophila psittaci, Chlamydophila abortus, Chlamydophila caviae) generally infect cats, birds, sheep, and guinea pigs, respectively. Serologic study results have been suggestive of the existence of multiple strains of C. felis that may differ in virulence. 4,5 However, the exact sites of antigenic variation in C. felis are unknown. 6 8 Chlamydial EBs survive only a few days at room temperature, although survival for up to 1 month at 4 C may be possible. 1 They are inactivated by lipid solvents and detergents but are somewhat resistant to acids and alkalis. PATHOGENESIS Much remains unknown regarding the pathogenesis of chlamydial infections in cats. Chlamydiae appear to have a predilection for conjunctival epithelial cells. Natural transmission of C. felis, like that of other respiratory pathogens, presumably occurs mainly by close contact with other infected cats and their aerosols and via fomites. Venereal transmission of chlamydiae occurs in several host species but has not been confirmed in cats. Infections caused by chlamydiae tend to follow a chronic, insidious course, often progressing through asymptomatic stages. In cats, conjunctivitis associated with C. felis may persist for several months. Organisms have been isolated from the conjunctiva for up to 215 days after experimental infection, although most cats cease conjunctival shedding at around 60 days after infection. 9,10 Persistent chlamydial infections are poorly understood, although RBs with atypical morphology have been identified in humans with chronic chlamydial diseases (e.g., reactive arthritis). Such infections are often culture negative and may be resistant to antimicrobial therapy. 11 The intestinal tract may be a site of persistent infection in cats, as has been shown in birds and ruminants. In cats with experimentally induced chlamydial conjunctivitis, prolonged rectal and vaginal C. felis excretion have been documented. 9 C. felis has also occasionally been found in the spleen, liver, and peritoneum of cats. The significance of the presence of organisms in these locations remains unclear. 12 14 Chlamydial disease may be exacerbated by superinfection with other microorganisms. In one study, 8% of cats had both chlamydial and either FCV or FHV1 infection. 15 Cats with concurrent FCV infection usually have other signs (e.g., oral ulceration) in addition to conjunctivitis. Dual infection appears to be more common with FCV than with FHV1. Coinfection with feline immunodeficiency virus (FIV) prolongs conjunctivitis and chlamydial shedding; in cats with existing FIV infection, superinfection with C. felis may accelerate the clinical progression of FIV infection. 10 Both Mycoplasma species and Bordetella bronchiseptica can complicate C. felis infections. Other bacteria, including those that normally colonize the healthy conjunctival sac, can also act as secondary invaders and worsen disease. EPIDEMIOLOGY The prevalence of C. felis infection has been examined using a variety of assays in several geographic locations. The prevalence of C. felis in cats with URTD as determined by culture has ranged from 23% to 31%. 15,16 A prevalence of 14.3% (66 of 462) was determined by polymerase chain reaction (PCR) assay. 17 The prevalence of C. felis in asymptomatic cats is low. None of 50 cats was positive for the organism using culture, 18 and 1 of 95 cats was positive for the organism using the PCR assay. 17 Persistent chlamydial shedding after clinical signs have resolved may explain positive results in some asymptomatic cats. Cats 2 to 6 months of age are most likely to be infected with C. felis. 15,17 The prevalence is also high in cats 7 to 11 months of age. The prevalence of C. felis infection in kittens younger than 2 months of age is low, presumably because of passive immunity. Cats older than 5 years of age are least likely to be infected with C. felis. There is no clear breed or sex predilection. CLINICAL SIGNS Respiratory and Ocular Disease Chlamydophila felis is primarily a conjunctival pathogen capable of causing acute to chronic conjunctivitis with blepharospasm, chemosis, congestion, and a serous to mucopurulent ocular discharge without dyspnea or coughing after approximately 3 to 5 days of incubation (Figure 1). Transient pyrexia and reduced appetite may occur shortly after infection, although many cats remain well and continue to eat. Clinical signs improve after a few weeks, but mild conjunctivitis frequently persists for several months (Figure 2). The strain or route of infection may influence the extent of respiratory tract involvement. Mild and clinically insignificant pulmonary lesions may result from aerosol exposure. 19 Nasal discharge and sneezing occur in some cats. Signs of rhinitis without concurrent ocular in- CHRONIC INSIDIOUS COURSE SUPERINFECTION CONJUNCTIVITIS
Compendium March 2001 Small Animal/Exotics 233 Figure 1 Severe conjunctivitis, chemosis, and serous ocular discharge associated with experimental Chlamydophila felis 6 days after infection. Figure 2 Chronic Chlamydophila felis infection with blepharospasm and serous to mucopurulent ocular discharge. volvement are highly unlikely to be associated with C. felis infection, 17 and involvement of other organisms (e.g., respiratory viruses) should be suspected. Chlamydophila felis infection is rarely associated with corneal damage. Although corneal involvement has been reported, these reports did not always exclude the possibility of a mixed infection involving such pathogens as FHV1. 20,21 One study showed that simultaneously inoculating a Streptococcus species isolate with C. felis was more likely to be associated with keratoconjunctivitis. 22 The ability of the organism to cause corneal disease may also depend on strain or host factors. Chlamydophila felis has occasionally been isolated from neonatal conjunctivitis in kittens, 8,23 although maternal antibody seems to protect most kittens until they are 9 to 12 weeks of age. Reproductive Tract Disease Causal relationships between chlamydial infections and reproductive disease have been recognized in many host species. C. felis has been suspected as a cause of abortion, neonatal mortality, and infertility in catteries, but a definite causative link has not been reported. Intravaginal and intraurethral chlamydiae inoculation has been associated with vaginal discharge, bleeding, and swelling in females; urethritis and urethral discharge in males; and proctitis in both sexes. 20,22 Directly inoculating C. felis into the oviducts led to salpingitis and growth of the organism in this location for weeks, with minimal systemic signs. 24 Vaginal discharge and shedding of chlamydiae from the vagina occur in some cats infected via the conjunctivae. 9,10,25 Placental tissue infection was demonstrated by PCR assay in a cat that was experimentally infected with C. felis by conjunctival inoculation during gestation. Placentitis was not observed histologically, and no evidence of infection was detected in the neonates. The queen experienced apparently normal parturition, but vaginal shedding of C. felis began immediately afterward. C. felis infection may be influenced by changes in the host s endocrine environment, as has been shown for other host species. Despite these findings, results of studies of naturally infected cats suggest that C. felis is unlikely to be an important cause of feline reproductive disease. Infertility and abortion have been equally distributed between infected and uninfected cat colonies, 26 and many Chlamydia-infected colonies do not have reproductive problems. FHV1 may be responsible for many suspected cases of C. felis induced genital and perinatal disease. FHV1 was detected in four of eight cats with combined reproductive disease and URTD in a large epidemiologic survey of cats with URTD, whereas C. felis was not detected. 17 If there is an association, the ability of C. felis to cause reproductive disease may depend on such factors as the stage of pregnancy when infection occurs, coinfection with other organisms, concurrent immunosuppression, route of infection, and the strain involved. Other Manifestations Chlamydial infection has been associated with peritonitis in a mature female cat. 13 Chlamydiae were also observed in the gastric mucosa of 12 young cats from five related research or commercial breeding colonies. 27 Four of the cats showed signs of weight loss of undetermined cause. Administering the organism to cats by aerosol and oral inoculation resulted in conjunctivitis, rhinitis, and (in some cats) mild gastritis. An association between chlamydial infection and lameness in cats has also been suggested. 8,28 Further studies are required to determine whether C. felis is capable of causing lameness in cats. CORNEAL INVOLVEMENT C. felis AND REPRODUCTIVE DISEASE ASSOCIATION WITH OTHER CONDITIONS
234 Small Animal/Exotics Compendium March 2001 Figure 3 Swabbing technique for collecting diagnostic samples of feline chlamydiosis. DIAGNOSIS Chlamydial infection needs to be differentiated from other causes of feline URTD. Accurate diagnosis requires some form of microbiologic assay. Unless the target of the assay is antibodies, most available diagnostic tests are designed to be conducted on conjunctival swabs (Figure 3). Examining Giemsa-stained conjunctival smears for chlamydial inclusions is not recommended as a reliable means of diagnosing feline chlamydial infection. Inclusions are generally only visible early in the course of infection and sometimes not at all. 9 False-positive results may be obtained when melanin granules in the cytoplasm of conjunctival cells are mistaken for organisms. In unvaccinated cats, serum antibody titers detected using indirect immunofluorescence correlate well with recent infection. Ninety-six percent of cats infected with C. felis have titers greater than 32, whereas only 7.5% of uninfected cats have titers that high. 15 However, the availability of this assay is limited, antibodies induced by vaccination may interfere with interpreting the assay, and acute and convalescent phase sera may be required to obtain a diagnosis in acute cases. The complement fixation test is unreliable in detecting recent C. felis infection. 29 Several ELISA antigen kits are available for diagnosing human Chlamydia trachomatis infection. Their sensitivities and specificities for detecting C. felis are extremely variable. One assay had a specificity of 90% and a sensitivity of only 79% when compared with cell culture for detecting C. felis, 30 whereas another had very poor sensitivity (25%) and specificity (84%) when compared with fluorescent antibody testing. 26 The gold standard for chlamydial diagnosis is cell culture, which most commonly uses fluorescent antibodies to detect intracytoplasmic chlamydial inclusions after inoculating cell monolayers. This is more sensitive than is directly applying fluorescent antibody to smears of affected tissue. Conjunctival swabs must be placed in special transport media containing appropriate antimicrobials to preserve chlamydial viability. Isolation in cell culture is technically demanding, time consuming, and expensive. Transportation and storage problems can affect the sensitivity of cell culture. The sensitivity of culture may vary among laboratories depending on equipment and technical expertise. Diagnostic PCR assays are now used routinely for diagnosing human chlamydial infections, and assays for C. felis are becoming increasingly available. PCR assays have been shown to have good sensitivity and specificity with proper sample collection and storage, 25 although the sensitivity of PCR assays may vary among laboratories. Because C. felis does not need to be viable for detection, special transport media are not required. False-positive results may be obtained from contamination before or after sample submission to the laboratory. Veterinarians collecting samples for PCR assay should contact the laboratory for sample collection and handling guidelines to minimize contamination. TREATMENT The drug of choice to treat chlamydial infections in cats is doxycycline. Other tetracyclines are also effective. In experimentally infected cats, acute C. felis infection was successfully treated using oral doxycycline for 3 weeks (5 mg/kg every 12 hours). 25 Topical treatment was not required. Rapid clinical improvement occurred within 2 days of the start of treatment. Organisms could not be detected using PCR assay and culture after day 6. Because of the long half-life of doxycycline, once-daily administration at 10 mg/kg is likely to be equally effective and more convenient for owners. Despite these results, sometimes treatment for longer than 3 weeks has been necessary to resolve natural C. felis infections. Some authors have recommended combining systemic therapy with topical tetracycline ointments every 6 to 8 hours. 31 33 A minimum of 6 to 8 weeks of treatment, especially in catteries, has also been suggested. 31,34 Continuing treatment for 2 weeks after clinical signs have resolved is generally recommended. Cats in two catteries were successfully treated with infeed lincomycin spectinomycin (55 and 111 mg/cat/day for 8 weeks, respectively). 26 Chlamydiae are also susceptible to erythromycin, rifampin, fluoroquinolones, and the newer macrolide azithromycin, but these drugs have not been evaluated for treating feline chlamydiosis. Thus far, clinically significant antimicrobial resistance has not been reported. Sulfonamides and chloramphenicol are ineffective against C. felis. Penicillin is inhibitory at high doses but does not eliminate the organism. DIAGNOSTIC DIFFERENTIALS CELL CULTURE DOXYCYCLINE
Compendium March 2001 Small Animal/Exotics 235 Chlamydophila felis may be more difficult to eliminate in chronic infections, as occurs in humans with chlamydial arthritis. 11 However, recurring cases often involve many cats and poor compliance; often, all cats are not treated and the owner fails to administer all doses. All cats must be treated with the full course of antimicrobials, and proper hygiene and quarantine must be maintained. This may be difficult to achieve when many cats must be treated. Clinicians must consider concurrent presence of the viral causes of URTD, which may show initial response to antimicrobial therapy because secondary bacterial infections may resolve. Use of a 1:32 bleach:detergent solution is recommended for general environmental disinfection when undiagnosed FCV infection remains a possibility. There is a risk of permanent teeth discoloration in kittens if tetracyclines are used in pregnant queens in the last 2 to 3 weeks of pregnancy or in kittens in the first few months of life. Doxycycline has reduced calcium-binding avidity compared with other tetracyclines and therefore produces only minor discoloration. Little evidence suggests that such side effects occur in cats receiving doxycycline, but owners should be made aware of the possibility. In humans, erythromycin is substituted, but there have been no studies on the effect of erythromycin in cats with chlamydiosis. Of the tetracyclines, doxycycline also has a lower risk of other side effects (e.g., gastrointestinal disturbances, exacerbating or producing renal disease). VACCINATION AND IMMUNITY Immunity to chlamydial infection is generally weak or short-lived. Although protection from rechallenge occurs 3 months after initial challenge, further protection is only partial. 9 However, the apparent age-related resistance of cats to C. felis infection is suggestive of some form of protective immunity eventually developing. Cell-mediated immunity appears essential for resolving infection. Both modified-live and inactivated cell culture vaccines have been used, either alone or in combination with feline panleukopenia, FCV, and FHV1 components. C. felis vaccines have been associated with atypical reactions (fever, lethargy, anorexia, lameness) 7 to 21 days after vaccination in approximately 3% of cats. 35 The chlamydial vaccine does not prevent infection or clinical signs, although the latter are generally reduced in severity. Both the chlamydial vaccine and the recently introduced intranasal B. bronchiseptica vaccine are only indicated for cats at demonstrable risk of acquiring infection and thus are considered noncore vaccines. 35 This is in contrast to the FCV and FHV1 vaccines, which are considered core vaccines because of SIDE EFFECTS OF DRUGS ATYPICAL REACTIONS
238 Small Animal/Exotics Compendium March 2001 the high prevalence of disease caused by these viruses and the relative refractoriness of viral URTD to treatment. The chlamydial and B. bronchiseptica vaccines are most beneficial as part of a control program in catteries or shelters where the disease is endemic. Because the maximum duration of immunity of these vaccines is not known, the recommendation is to administer booster vaccinations annually to cats that are at risk of acquiring these infections. ZOONOTIC POTENTIAL Chlamydophila felis has been implicated in conjunctivitis in humans, but evidence to support this association has not been strong. One report involved a man with unilateral follicular conjunctivitis. His 12-weekold kitten, which slept on his bed, also had a unilateral ocular discharge. 36,37 The man lived in a crowded boarding house with several other humans, cats, dogs, and monkeys. Chlamydiae were isolated from the kitten and the affected human and distinguished from the human pathogen C. trachomatis by their failure to uptake iodine. However, in another report, only 19% (4 of 21) of cat owners with chlamydial conjunctivitis complained of recent itchy or sore eyes compared with 25% (2 of 8) of cat owners negative for C. felis. 9 C. felis has also been associated with other diseases in humans, including hepatosplenomegaly, glomerulonephritis, and endocarditis. 38,39 In all these cases, associations were made on the basis of serology, which is not species specific. The pathogen involved in some or all of these cases was possibly the recently discovered C. pneumoniae, which also fails to stain with iodine. If C. felis is zoonotic, maintenance of hygienic conditions is probably adequate to prevent human disease, although further investigation of the zoonotic potential of this organism is needed. Chlamydia has also been implicated via serology in cat-scratch disease in humans, 40 which is now known to be caused by Bartonella henselae and Bartonella clarridgeiae. Recent studies have described serologic crossreactions between Bartonella and Chlamydia species 41 that may be responsible for the erroneous interpretations of Chlamydia in cat-scratch disease. In addition, bartonellosis cannot be ruled out as a cause of such clinical manifestations as endocarditis and glomerulonephritis in humans diagnosed with chlamydiosis on the basis of serology. About the Author Dr. Sykes is affiliated with the Department of Small Animal Clinical Sciences, University of Minnesota, St. Paul. ACKNOWLEDGMENT This article is based on a chapter by the same author in Feline Medicine and Therapeutics, ed 3, and has been adapted with kind permission from Blackwell Science Ltd, Oxford. REFERENCES 1. Baker JA: A virus obtained from a pneumonia of cats and its possible relation to the cause of atypical pneumonia in man. Science 96:475 476, 1942. 2. Hamre D, Rake G: Feline pneumonitis (Baker), a new member of the lymphogranuloma-psittacosis group of agents. J Infect Dis 74:208 211, 1944. 3. Everett KD, Bush RM, Andersen AA: Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms. Int J Syst Bacteriol 49 Pt 2:415 440, 1999. 4. Yerasimides TG: Isolation of a new strain of feline pneumonitis virus from a domestic cat. J Infect Dis 106:290 296, 1960. 5. Kuroda-Kitogawa Y, Suzuki-Muramatsu C, Yamaguchi T, et al: Antigenic analysis of Chlamydia pecorum and mammalian Chlamydia psittaci by use of monoclonal antibodies to the major outer membrane protein and a 56- to 64-kd protein. Am J Vet Res 54:709 712, 1993. 6. Sayada C, Andersen A, Rodriguez P, et al: Homogeneity of the major outer membrane protein gene of feline Chlamydia psittaci. Res Vet Sci 56(1):116 118, 1994. 7. May SW, Kelling CL, Sabara M, et al: Virulence of feline Chlamydia psittaci in mice is not a function of the major outer membrane protein (MOMP). Vet Microbiol 53:355 368, 1996. 8. Sykes JE: Improvements in Diagnosis and Understanding of Feline Upper Respiratory Tract Pathogens (PhD Thesis). University of Melbourne, 1997. 9. Wills JM: Chlamydial infection in the cat (PhD Thesis). University of Bristol, 1986. 10. O Dair HA, Hopper CD, Gruffydd-Jones TJ, et al: Clinical aspects of Chlamydia psittaci infection in cats infected with feline immunodeficiency virus. Vet Rec 134(15):365 368, 1994. 11. Leirisalo-Repo M: Are antibiotics of any use in reactive arthritis? APMIS 101(8):575 581, 1993. 12. Baker JA: A virus causing pneumonia in cats and producing elementary bodies. J Exp Med 79:159 171, 1944. 13. Dickie CW, Sniff ES: Chlamydia infection associated with peritonitis in a cat. JAVMA 176:1256 1259, 1980. 14. Hoover EA: Feline pneumonitis, in Kirk RW (ed): Current Veterinary Therapy VII, Small Animal Practice. Philadelphia, WB Saunders Co, 1980, pp 1299 1302. 15. Wills JM, Howard PE, Gruffydd-Jones TJ, et al: Prevalence of Chlamydia psittaci in different cat populations in Britain. J Small Anim Pract 29:327 339, 1988. 16. Hanselaer JR, Derore A, Boucherie P, et al: Demonstration of Chlamydia psittaci in feline conjunctivitis cases in Belgium. Vlaams Diergeneeskd Tijdschr 58:165 168, 1989. 17. Sykes JE, Anderson GA, Studdert VP, et al: Prevalence of feline Chlamydia psittaci and feline herpesvirus-1 in cats with upper respiratory tract disease. J Vet Intern Med 13(3): 153 162, 1999.
240 Small Animal/Exotics Compendium March 2001 18. Shewen PE, Povey RC, Wilson MR: A survey of the conjunctival flora of clinically normal cats and cats with conjunctivitis. Can Vet J 21(8):231 233, 1980. 19. Hoover EA, Kahn DE, Langloss JM: Experimentally induced feline chlamydial infection (feline pneumonitis). Am J Vet Res 39:541 547, 1978. 20. El-Sheikh EHA: Feline Chlamydial Keratoconjunctivitis as an Analogue of Trachoma (PhD Thesis). University of London, 1978. 21. Tabatabayi AH, Rad MA: First isolation of feline C. psittaci from a cat in Iran. Feline Pract 11:35 38, 1981. 22. Darougar S, Monnickendam MA, El-Sheikh H, et al: Animal models for the study of chlamydial infections, in Hobson D, Holmes KK (eds): Non-Gonococcal Urethritis and Related Infections. Washington DC, American Society for Microbiology, 1977, pp 186 198. 23. Wills JM, Gaskell RM: Feline chlamydial infection, in Chandler EA, Gaskell CJ, Gaskell RM (eds): Feline Medicine and Therapeutics, ed 2. Oxford, Blackwell Science Ltd, 1994, pp 544 551. 24. Kane JL, Woodland RM, Elder MG, et al: Chlamydial pelvic infection in cats: A model for the study of human pelvic inflammatory disease. Genitourin Med 61:311 318, 1985. 25. Sykes JE, Studdert VP, Browning GF: Polymerase chain reaction detection of Chlamydia psittaci in untreated and doxycycline-treated experimentally infected cats. J Vet Intern Med 13(3):146 152, 1999. 26. Pointon AM, Nicholls JM, Neville S, et al: Chlamydia infection among breeding catteries in South Australia. Aust Vet Pract 21:58 63, 1991. 27. Hargis AM, Prieur DJ, Gaillard ET: Chlamydial infection of the gastric mucosa in twelve cats. Vet Pathol 20(2):170 178, 1983. 28. TerWee J, Sabara M, Kokjohn K, et al: Characterization of the systemic disease and ocular signs induced by experimental infection with Chlamydia psittaci in cats. Vet Microbiol 59(4):259 281, 1998. 29. Cello RM: Microbiological and immunological aspects of feline pneumonitis. JAVMA 158:932 938, 1971. 30. Wills JM, Millards WG, Howard PE: Evaluation of a monoclonal antibody based ELISA for detection of feline Chlamydia psittaci. Vet Rec 119:418 420, 1988. 31. Greene CE: Chlamydial infections, in Greene CE (ed): Infectious Diseases of the Dog and Cat, ed 2. Philadelphia, WB Saunders Co, 1998, pp 172 174. 32. Gaskell RM: Upper respiratory disease in the cat (including chlamydia): Control and prevention. Feline Pract 21:29 34, 1993. 33. Gaskell RM, Bennett M: Feline and Canine Infectious Diseases. Oxford, Blackwell Science Ltd, 1996, pp 21 25. 34. Gruffydd-Jones TJ, Jones BR, Hodge H, et al: Chlamydia infection in cats in New Zealand. NZ Vet J 43:201 203, 1995. 35. Elston T, Rodan I: Feline vaccination guidelines. Compend Contin Educ Pract Vet 20(8):936 941, 1998. 36. Ostler HB, Schachter J, Dawson CR: Acute follicular conjunctivitis of epizootic origin. Arch Ophthalmol 82:587 591, 1969. 37. Schachter J, Ostler HB, Meyer KF: Human infection with the agent of feline pneumonitis. Lancet 1:1063 1065, 1969. 38. Griffiths PD, Lechler RI, Treharne JD: Unusual chlamydial infection in a human renal allograft recipient. BMJ 2(6147): 1264 1265, 1978. 39. Regan RJ, Dathan JRE, Treharne JD: Infective endocarditis with glomerulonephritis associated with cat chlamydia (Chlamydia psittaci) infection. Br Heart J 42:349 352, 1979. 40. Emmons RW, Riggs JL, Schachter J: Continuing search for the etiology of cat scratch disease. J Clin Microbiol 4(1):112 114, 1976. 41. Maurin M, Eb F, Etienne J, et al: Serological cross-reactions between Bartonella and Chlamydia species: Implications for diagnosis. J Clin Microbiol 35(9):2283 2287, 1997. ARTICLE #2 CE TEST The article you have read qualifies for 1.5 contact hours of Continuing Education Credit from the Auburn University College of Veterinary Medicine. Choose the one best answer to each of the following questions; then mark your answers on the test form inserted in Compendium. 1. Chlamydiae are a. viruses. b. gram-negative bacteria. c. gram-positive bacteria. d. rickettsiae. e. mycoplasmas. 2. At room temperature, chlamydiae generally survive a. a few days. b. a few months. c. up to 1 year. d. a few hours. e. no more than a few minutes outside the host because they are located intracellularly. 3. Chlamydiae have been detected in from experimentally infected cats. a. oropharyngeal, conjunctival, and rectal swabs b. rectal and conjunctival swabs and blood samples c. rectal, vaginal, and conjunctival swabs d. conjunctival and vaginal swabs and blood samples e. oropharyngeal, conjunctival, and vaginal swabs 4. Which of the following statements regarding the pathogenesis of feline chlamydiosis is false? a. Mixed infections with other respiratory pathogens occur occasionally and may worsen clinical signs. b. Venereal transmission is the most common, although fomites and aerosol transmission may also play a role. c. C. felis may occasionally disseminate to abdominal viscera. d. Chlamydial shedding may be prolonged in cats coinfected with FIV. e. Cats may shed chlamydiae for as long as 7 months after infection.
Compendium March 2001 Small Animal/Exotics 241 5. Chlamydiosis is most likely to be documented in cats of age. a. younger than 5 weeks d. 1 to 5 years b. 2 to 11 months e. older than 15 years c. 5 to 10 years 6. Which of the following statements regarding clinical manifestations of feline chlamydiosis is true? a. C. felis commonly causes reproductive failure in cats. b. C. felis can cause rhinitis without signs of conjunctivitis. c. Cats with chlamydiosis commonly show signs of inappetence and lethargy throughout the course of illness. d. C. felis is rarely associated with keratitis in cats. e. Transient lameness occurs commonly in cats infected with C. felis. 7. In general, which of the following is the most unreliable diagnostic test for feline chlamydiosis? a. serology using indirect immunofluorescence b. conjunctival cytology c. direct fluorescent antibody test d. cell culture e. PCR assay 8. Which of the following statements regarding diagnosis of feline chlamydiosis is false? a. The gold standard for chlamydial diagnosis is cell culture. b. The main disadvantage of the PCR assay is the potential for false-positive results caused by contamination. c. Antigen-detection ELISA kits for detecting human C. trachomatis infections may cross-react with C. felis and can be used for diagnosing feline chlamydiosis. d. The complement fixation test is unreliable in detecting chlamydial infection. e. Samples for diagnosis via PCR assay must be shipped carefully in appropriate transport media to preserve chlamydial viability. 9. The treatment of choice for feline chlamydiosis is a. erythromycin. d. azithromycin. b. chloramphenicol. e. sodium penicillin. c. doxycycline. 10. Which of the following statements regarding C. felis is true? a. C. felis is frequently isolated from asymptomatic cats because of the carrier state. b. Cat-scratch disease may be caused by C. felis and B. henselae. c. C. felis infection can be prevented by vaccination. d. Several antibiotic-resistant strains of C. felis have been documented. e. Evidence to support a causal role for C. felis in human conjunctivitis is weak.