Feline ocular chlamydiosis: clinical and microbiological effects of topical and systemic therapy

Conjunctival swabs taken from a two-month-old kitten showing ocular discharge were found to be positive for Chlamydophila felis by PCR and isolation. The cat was treated with topical 1% tetracycline ophthalmic ointment twice a day for 60 days. At the end of the treatment, the cat showed no ocular signs and conjunctival swabs resulted PCR and isolation negative for C. felis. Forty days later, the ocular discharge recurred and C. felis was isolated from conjunctival swabs taken from both the cat's eyes. Twenty days of doxycycline systemic treatment at 10 mg/kg once daily was started. The treatment resulted in a complete clinical recovery after a few days. C. felis was not isolated or amplified on the 10th day after beginning the treatment. The cat's conjunctival swabs were also PCR and isolation negative on the 10th, 30th, 60th, 90th, 120th and 240th days after the end of therapy.

CpG motifs as adjuvant in DNA vaccination against Chlamydophila psittaci in turkeys

Plasmid DNA (pcDNA1::MOMP) expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain and recombinant MOMP (rMOMP) with or without the immunomodulating CpG oligonucleotides (CpG ON) were tested for their ability to elicit an immune response and to induce protection in turkeys against homologous challenge. Two CpG ON were chosen for in vivo application based on their in vitro capacity to stimulate the production of nitric oxide (NO) in chicken macrophages and their in vitro capacity to induce turkey lymphocyte proliferation. Priming and boosting of turkeys with pcDNA1::MOMP was able to prevent severe clinical signs and bacterial replication in a turkey model of C. psittaci infection. rMOMP boosting induced high antibody titers, but these did not correlate with the level of protection. Although the CpG ON induced a significant in vitro response, the presence of the CpG ON as an adjuvant generated no significant effect on the immune response or on the protective capacity of the tested vaccination methods.

Is Chlamydophila felis a significant zoonotic pathogen?

PROBLEM

Chlamydophila felis is a common cause of conjunctivitis in cats and in some textbooks is listed as an important zoonotic pathogen. However, there are no published comprehensive reviews assessing the evidence supporting this. SEARCH AND ANALYSIS: Bibliographic databases and bibliographies of papers and textbooks were searched for all published cases of zoonotic disease associated with chlamydiosis in cats. All published case reports were reviewed to establish the quality of the evidence supporting the association between C. felis and zoonotic disease.

RESULTS

There are only seven case reports, most of which were published before the development of assays capable of distinguishing C. felis from other chlamydial species, implicating this organism in zoonotic disease. None of the three cases of pneumonia and systemic disease described, two of which occurred in immunocompromised patients, can be unambiguously attributed to C. felis. Of the four cases of follicular keratoconjunctivitis described, only one, in an immunocompromised patient, could be unambiguously attributed to C. felis.

CONCLUSION

While there is evidence that C. felis may occasionally cause keratoconjunctivitis in humans, there is little evidence to suggest it can cause serious systemic disease or pneumonia.

Factors associated with upper respiratory tract disease caused by feline herpesvirus, feline calicivirus, Chlamydophila felis and Bordetella bronchiseptica in cats: experience from 218 European catteries

A full history of the management practices and the prevalence of upper respiratory tract disease (URTD) at 218 rescue shelters, breeding establishments and private households with five or more cats was recorded. Oropharyngeal and conjunctival swabs and blood samples were taken from 1748 cats. The prevalences of feline herpesvirus (FHV), feline calicivirus (FCV), Chlamydophila felis and Bordetella bronchiseptica were determined by PCR on swab samples. An ELISA was applied to determine the prevalence of antibodies to B. bronchiseptica. The rates of detection by PCR of each pathogen in the cats in catteries with and without ongoing URTD were, respectively, FHV 16 per cent and 8 per cent; FCV 47 per cent and 29 per cent; C. felis 10 per cent and 3 per cent; and B. bronchiseptica 5 per cent and 1.3 per cent; the seroprevalences of B. bronchiseptica were 61 per cent and 41 per cent, respectively. There was evidence that FHV, FCV and B. bronchiseptica played a role in URTD. The risk factors associated with the disease were less than excellent hygiene, contact with dogs with URTD, and larger numbers of cats in the cattery or household.

Role of Chlamydophila abortus in ovine and caprine abortion in Sardinia, Italy

Between 1999-2003, 14321 sera and 646 abortion samples (498 foetuses and 148 placentae) were analysed from 807 sheep and goat farms distributed all over the island of Sardinia. After notification of abortion in a flock, sera collected at random from adult animals were examined to detect antibodies specific to Chlamydophila (C.) abortus by ELISA, whereas foetuses and placenta were analysed by PCR assay. Specific IgG antibodies were detected in 611 (4.8%) sheep and 106 (5.8%) goats. From a total of 2050 ovine and 151 caprine fetal samples including muscle, liver, abomasum, spleen, brain and placenta, 29 (1.4%) ovine and 1 (0.6%) caprine samples were C. abortus PCR-positive. Placenta was the tissue with the highest detection rate. These results indicate that the seroprevalence of C. abortus infection in sheep and goats is very low in Sardinia, and PCR results demonstrate that C. abortus has no significant role in abortion, especially in goats.

Bovine Chlamydophila spp. infection: do we underestimate the impact on fertility?

Classical methods for detection of Chlamydophila species, and of antibodies against these agents, have indicated that these bacteria are highly prevalent in cattle and associated with numerous disease conditions. These methods demonstrated acute Chlamydophila-induced diseases such as epizootic bovine abortion, as well as worldwide variable, but generally high, Chlamydophila seroprevalence. However, it was impossible to consistently detect the low levels of these organisms which were suspected to be present in endemic infections. Application of highly sensitive real-time PCR and ELISA methods for detection of Chlamydophila spp. DNA and of antibodies against Chlamydophila spp., respectively, in a series of prospective cohort studies revealed a high prevalence of Chlamydophila spp. genital infections in female calves (61%) and adult heifers (53%). These infections were acquired by extragenital transmission in the first weeks of life, and infection frequency was increased by crowding of the animals. A challenge study demonstrated that infection with C. abortus resulted in decreased fertility of heifers. The experimental use of a C. abortus vaccine provided evidence for immunoprotection against C. abortus-induced suppression of bovine fertility. The results of these investigations suggest that bovine Chlamydophila infection should be viewed more as pervasive, low-level infection of cattle than as rare, severe disease. Such infections proceed without apparent disease or with only subtle expressions of disease, but potentially have a large impact on bovine herd health and fertility.

Diagnosis of ovine chlamydial abortions by PCR-RFLP performed on vaginal swabs

Ovine enzootic abortion is an infectious and contagious disease clinically characterized by abortion and weak neonates, affecting sheep and goats. The etiological agent is Chlamydophila (C.) abortus, which is considered one of the most common animal pathogens of small ruminants; it has important economic implications and represents a significant zoonotic risk. Clinical diagnosis is often difficult because the clinical signs and the pathological lesions are not specific for C. abortus infection, in fact they can also be observed as a result of infections with other abortifacient agents. Moreover, the involvement of the laboratory is necessary to perform the definitive diagnosis. One hundred and seventeen vaginal swabs from sheep with clinical signs related to chlamydial infection were examined by a PCR-RFLP assay that demonstrated high specifity and sensitivity. Six samples were positive for C. abortus. Vaginal swabs are easy to handle and allow to deal with biohazardous material in safety conditions.

High prevalence of chlamydial (Chlamydophila psittaci) infection in fetal membranes of aborted equine fetuses

Seventy-seven cases of equine abortion from 49 Hungarian farms that occurred between 1998 and 2000 were investigated for the presence of chlamydiae by immunohistochemistry, PCR and/or MZN staining. Evidence of the presence of these bacteria was obtained in 64 cases (83.1%) from 41 (83.7%) different farms. Partial ompA gene sequencing of PCR products revealed that the agent was Chlamydophila psittaci. Based on the findings of microbial diagnosis, pathology and case history, chlamydial infection was considered to be the most likely cause of abortion in at least 11 (14.3%) cases. In the remaining 53 Chlamydophila-positive cases, either other bacterial and viral agents (n = 22 or 28.6%) as well as non-infectious factors (n = 14 or 18.2%) were identified as more probable primary causes of disease, or the role of chlamydiae remained unclear because lesions in fetuses and fetal membranes were absent (n = 17 or 22.1%). When chlamydial antigen was detected in aborted equine placental tissue using immunohistochemistry it was seen only in the chorionic epithelial cells, but not in other parts of the fetal membranes nor in any of the fetal tissues. In conclusion, chlamydial infection of the genital tract should be considered a possible factor in equine reproductive disorders.

Use of quantitative real-time PCR to monitor the response of Chlamydophila felis infection to doxycycline treatment

Fifteen cats infected with Chlamydophila felis were monitored for the presence of C. felis DNA on ocular swabs by using real-time PCR and for clinical signs of disease. The cats were assigned to three groups: oral doxycycline at 10 mg/kg of body weight/day for 7 days (six cats), oral doxycycline at 10 mg/kg/day for 14 days (five cats), and an untreated control group (four cats). The untreated cats remained positive for C. felis throughout the trial; clinical signs were most severe on days 14 to 21 postinfection, and then they declined. Treatment with 7 and 14 days of doxycycline decreased C. felis relative copy numbers and clinical signs rapidly. C. felis became undetectable in some of the cats during or after treatment. However, after the cessation of treatment, a recurrence of high relative copy numbers of C. felis and severe clinical signs in all cats was seen. Rescue treatment with 21 days of doxycycline was successful at eliminating infection in eight of the cats; a further 28 days of doxycycline was required to eliminate infection in the remaining three cats. It was concluded that 7, 14, and, in some cases, 21 days of treatment with oral doxycycline will not eliminate C. felis infection. At least 28 days of treatment with doxycycline is required to ensure elimination of the organism. Real-time PCR is a sensitive technique for monitoring C. felis infection and the response to antibiotic treatment.

Feline Chlamydiosis

Chlamydiae are an important cause of acute and chronic conjunctivitis in cats. Until recently, only one organism was thought to infect cats, Chlamydophila felis (previously Chlamydia psittaci var. felis). Recently, other Chlamydia-like organisms belonging to the family Parachlamydiaceae, which comprises organisms that reside and proliferate within free-living amoeba, have been identified in cats with neutrophilic and eosinophilic conjunctivitis. The relative importance of these organisms and their amoebic hosts requires investigation. There is also weak evidence that chlamydiae may also be capable of causing reproductive tract disease and lameness in cats. Diagnosis of chlamydial conjunctivitis requires use of specialized culture techniques or the polymerase chain reaction. The antibiotic of choice to treat these infections is doxycycline; azithromycin is less effective. All cats in the household should be treated simultaneously. The zoonotic potential of these organisms appears low, but some precaution is warranted when handling affected cats.

Molecular characterisation and ovine live vaccine 1B evaluation toward a Chlamydophila abortus strain isolated from springbok antelope abortion

Chlamydiosis is a zoonosis with a worldwide distribution. The reservoir of susceptible hosts is large and includes birds and both domestic and wild mammals. Chlamydial infection, determined serologically, seems to be widespread among wild ruminants in the Paris zoo (France). In February 2003, an abortion case was reported within the springbok (Antidorcas marsupialis) herd of the zoo. PCR assay using primers targeting the polymorph membrane protein gene (pmp) family was performed on both vaginal swab and placenta samples revealing the presence of Chlamydophila. The inoculation into chicken embryos of an infected placenta extract led to the successful isolation of a C. abortus strain referred to as ASb1. The omp1 gene coding the major outer membrane protein (momp) and the 16S-23S rRNA spacer region of ASb1 were compared to those of various strains by restriction fragment length polymorphism (RFLP). The RFLP analysis showed that this isolate belonged to Chlamydophila abortus species and is highly related to known domestic ruminant's strains causing abortion. The efficacy of a live vaccine 1B, based on a temperature-sensitive mutant of the ovine abortion reference strain AB7, was tested. Protection-challenge experiments in a mouse model show that the ASb1 strain led to mice abortions and that vaccination with 1B vaccine provided them with effective protection.

Detection of Chlamydophila abortus in sheep and goat flocks in southern Italy by PCR using four different primer sets

An epidemiological survey was performed to detect the presence of Chlamydophila (C.) abortus and other members of the order Chlamydiales in ovine and caprine flocks with a history of abortion in southern Italy. Four pairs of primers were compared to evaluate their ability to detect Chlamydiales using purified DNA preparations and tissue samples from aborted foetuses with suspected chlamydial infections. As expected, amplification of DNA of the reference strain C. abortus using primer pairs U23F/23Sigr, 16SF2/23R, CTU/CTL and CpsiA/CpsiB produced fragments of about 600 bp, 585 bp, 1000 bp and 300 bp, respectively. The detection limits of the four PCR tests performed on serial DNA dilutions of the C. abortus reference strain were of 10 pg, 0.1 pg, 0.1 pg and 1 fg of DNA, respectively. The most sensitive amplification of DNA extracted from the organ tissues was obtained with primer pairs CpsiA/CpsiB, which detected Chlamydophila spp. DNA in all infected tissue samples. Only C. abortus was identified during the survey. The presence of this agent was confirmed in 3 out of 27 ovine and caprine flocks included in the survey suggesting that abortion due to C. abortus is uncommon in southern Italy.

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus

In an attempt to ascertain the means whereby previous exposure to Chlamydophila (C.) abortus can protect against the re-occurrence of enzootic abortion of ewes (EAE), ten previously-exposed ewes were intravenously rechallenged with a large infective dose of C. abortus during pregnancy. The patterns of development of chlamydial placentitis and its sequelae closely resembled that observed following first-time challenge of previously-naïve ewes, although placentitis appeared to develop more slowly following rechallenge infection and none of the rechallenged ewes aborted. Chorioallantoic and foetal pathology and foetal immune responses were qualitatively similar whilst the local maternal response to C. abortus infection of the endometrium did not appear to differ in rechallenged and first-time challenged sheep. This demonstrates that if C. abortus reaches the foetal side of the placenta, a stereotypical response is elicited, regardless of the status of maternal immunity. Therefore it appears that in natural circumstances, acquired immunity of the dam protects against the re-occurrence of EAE by preventing the causative agent from reaching the susceptible foetal trophoblast.

High prevalence of natural Chlamydophila species infection in calves

We investigated the acquisition and prevalence of Chlamydophila sp. infection in calves. Specimens were collected at weekly intervals from birth to week 12 postpartum from 40 female Holstein calf-dam pairs in a dairy herd. Real-time PCR detected, quantified, and differentiated Chlamydophila 23S rRNA gene DNA from vaginal cytobrush swabs and milk samples. Chemiluminescence enzyme-linked immunosorbent assay with lysed Chlamydophila abortus or Chlamydophila pecorum elementary body antigens quantified antibodies against Chlamydophila spp. in sera. Chlamydophila sp. DNA was found in 61% of calves and 20% of dams in at least one positive quantitative PCR. In calves, clinically inapparent C. pecorum infection with low organism loads was fivefold more prevalent than C. abortus infection and was most frequently detected by vaginal swabs compared to rectal or nasal swabs. In dams, C. abortus dominated in milk and C. pecorum dominated in the vagina. The group size of calves correlated positively (P < 0.01) with Chlamydophila infection in quadratic, but not linear, regression. Thus, a doubling of the group size was associated with a fourfold increase in frequency and intensity of Chlamydophila infection. For groups of 14 or 28 calves, respectively, logistic regression predicted a 9 or 52% probability of infection of an individual calf and a 52 or 99.99% probability of infection of the group. Anti-Chlamydophila immunoglobulin M antibodies in Chlamydophila PCR-positive calves and dams and in dams that gave birth to calves that later became positive were significantly higher than in PCR-negative animals (P </= 0.02). Collectively, crowding strongly enhances the frequency and intensity of highly prevalent Chlamydophila infections in cattle.

Immunopathology of Chlamydophila abortus infection in sheep and mice

Chlamydophila abortus targets the placenta, causing tissue damage, inflammation and abortion (enzootic abortion of ewes). It is one of the main infectious causes of abortion in ewes, resulting in major economic losses to agricultural industries worldwide. Although ruminants and pigs are the principal hosts, humans are also susceptible to infection. Control of disease requires a host inflammatory response, which is likely to contribute to pathology and abortion. Mouse models have been widely used to provide insight into the role of specific immune cells in controlling infection and disease. The use of such model systems for investigating the mechanisms of abortion, latency, persistence, and immunity to reinfection will result in the identification of novel vaccine control strategies for sheep.

Evaluation of different laboratory methods for diagnosis of pig chlamydiosis in Lithuania

Pig chlamydiosis is antrophozoonosis caused by Chlamydophila abortus. Chlamydias (C type) are widely found in nature and can infect humans, domestic and wild mammals, and 139 types of birds. The peculiar feature of chlamydias is the tropism to different tissues, organs and organisms. In 2502 pig blood sera tests from Lithuanian farms, anti-chlamydia complement binding (CB) antibodies were detected in 192 cases (7.7%). Serological tests showed the following (C type) chlamydia bearing regions: 22.0% Mazeikiai district, 17.2%--Kaisiadorys district, 13.5%--Panevezys district, 12.3%--Vilkaviskis district. Rare incidence of the disease was found in Siauliai district 1,2% and Klaipeda district 2.5% farms. The highest antibody titers in blood serum tests were found in Joint Stock Company (JSC) "Krekenava" and "Vejine", i.e. 1:128 and 1:64, respectively. The following methods for the study of pig chlamydiosis were used and comparatively evaluated: complement binding reaction (CBR), direct immunofluorescence (DIF), imunoenzyme assay (IEA), indirect immunofluorescense (IIF), micro immunofluorescense (MIF), polymerase chain reaction (PCR) and cell culture (CC) test. PCR method was found to be more sensitive and reliable compared to imunoenzyme assay, but the latter is more economic especially for screaning. In pigs with the clinically expressed symptoms, 108 pigs infected with chlamydia were detected. CB assay revealed the infection rate from 3.4% to 7.9% in piglets, sows and boars. The highest level of chlamydia infection was detected in fatteners (17.6%). Seroepizootic study of pig chlamydiosis revealed the different infection rate in the animals investigated. The highest chlamydia infection risk is in winter (10.4%) and the lowest--in summer (2.8%).

Vaccination against chlamydial infections of man and animals

Vaccination is the best approach for controlling the spread of chlamydial infections, in animal and human populations. This review summarises the progress that has been made towards the development of effective vaccines over the last 50 years, and discusses current vaccine strategies. The ultimate goal of vaccine research is to develop efficacious vaccines that induce sterile, long-lasting, heterotypic protective immune responses. To date, the greatest success has been in developing whole organism based killed or live attenuated vaccines against the animal pathogens Chlamydophila abortus and Chlamydophila felis. However, similar approaches have proved unsuccessful in combating human chlamydial infections. More recently, emphasis has been placed on the development of subunit or multicomponent vaccines, as cheaper, safer and more stable alternatives. Central to this is a need to identify candidate vaccine antigens, which is being aided by the sequencing of representative genomes of all of the chlamydial species. In addition, it is necessary to identify suitable adjuvants and develop methods for antigen delivery that are capable of eliciting mucosal and systemic cellular and humoral immune responses. DNA vaccination in particular holds much promise, particularly in terms of safety and stability, although it has so far been less effective in humans and large animals than in mice. Thus, much research still needs to be done to improve the delivery of plasmid DNA, as well as the expression and presentation of antigens to ensure that effective immune responses are induced.

Efficacy of different commercial and new inactivated vaccines against ovine enzootic abortion

The protective efficacy of two inactivated commercial (A, B) and two new inactivated vaccines (M7, QS) against ovine enzootic abortion was determined in two separate experiments in sheep. Vaccine A contained chlamydiae propagated in chicken embryos, adjuvated with Marcol 82, and vaccine B contained chlamydiae cultured in cell monolayers, adjuvated with aluminium hydroxide. For the preparation of the experimental vaccines, Chlamydophila abortus AB7 strain was cultured in McCoy cells and adjuvated with QS-21 (QS) or Montanide ISA 773 (M7). The ewes were vaccinated twice subcutaneously and challenged at 90 days of gestation. Protection was evaluated by clinical, bacteriological and serological examinations, and compared to two control groups: one of infected but not vaccinated ewes, and another of vaccinated but not infected ewes. The experimental vaccines induced considerably better protection than the two commercial ones. The new vaccine M7 especially showed no abortions, a good antibody response, the highest newborn lamb weights and the lowest level of C. abortus shedding at lambing.

Use of a duplex-PCR assay to screen for Feline Herpesvirus-1 and Chlamydophila spp. in mucosal swabs from cats

Fifty-four ocular and forty-six pharyngeal swabs, collected from 54 cats with respiratory syndrome, were analyzed by duplex-PCR to evaluate the presence of Feline Herpesvirus type 1 and Chlamydophila spp. Both pathogens are in the population of cats and as four cats were positive only in ocular swabs and three only in pharyngeal ones, it is deduced that a correct diagnostic approach has to foresee the dispatch to the laboratory of both swabs. Furthermore, all chlamydophila strains analysed by endonuclease restriction were classified as Chlamydophila felis.