| Chlamydia spp.are obligate intracellular gram-negative bacteria and spherical observed under microscope.When incubating well in vitro with chicken embryos and cell lines,these pathogens undergo a unique biphasic development cycle transitioning between the infectious,extracellular elementary body and the replicative,intracellular reticulate body.Chlamydia spp.can infect human and a wide variety of animals,including a number of economically important species,in all over the word as America,Europe,Asia,Africa and Oceania.The genus Chlamydia(Family:Chlamydiaceae)contains 12 speices,mainly C.trachomatis,C.pneumoniae,C.abortus,C.psittaci,C.suis,C.pecorum,C.felis,C.muridarum,C.caviae,C.ibidis,C.avium,C.gallinacea.Chlamydia psittaci was recognized as the only pathogen of avian chlamydiosis before the C.avium and C.gallinacea were detected in poultry from Europe countries and China recently.The infections of C.gallinacea in poultry were more popular than C.avium,while C.gallinacea with high prevalence in pigeons but C.avium with high positivity in chickens and turkey.Papers concerned on the prevalence,host specificity and genomics of C.gallinacea were reported recently.However,the mode of transmission of C.gallinacea was still unknown.In order to investigate the horizontal transmission mode of C.gallinacea in chickens,isolators connected outlet and inlet with air pipe were designed in this study.In the facilities,SPF chickens can infect through fecal-oral route by contacting with the food and drinking water contaminated with C.gallinacea,and aerosol-inhalation route by inhaling the air contaminated with C.gallinacea.In isolator I,SPF chickens contact the chickens infected with C.gallinacea and excretion produced by infected animals directly.The isolator III was connected with isolator with chickens positive for C.gallinacea through air pipe,while isolator II is negative control group.The results detected with FRET-qPCR showed that the chickens in isolator I(fecal-oral group)were positive for C.gallinacea after 15 days.The oral swabs and cloacal swabs from the aerosol group and negative-control group were negative for FRET-qPCR.The organs of chickens' elected randomly from aerosol group and negative-control group were negative for C.gallinacea.We detected nucleotides of C.gallinacea by FRET-qPCR from organs of chickens from infection group and fecal-oral group,mainly heart(2/10),lung(2/10),spleen(3/10),kidney(1/10),glandular stomach(3/10),duodenum(7/10),rectum(10/10),cloaca(10/10),ovary(1/10).In addition,the concentration of chlamydial DNA in duodenum,rectum and cloaca were higher than other organs.In order to investigate the mode of vertical transmission of C.gallinacea in chicken flow,cloacal swabs of breeding hens(n=100),cloacal swabs(n=28)and semen samples(n=28)of breed rosters,shell swabs of eggs(n=294),albumen samples(n=128)and yolk samples(n=128)were collected from commercial farm in Shaobo,Jiangsu province.In addition,organs(n=55/each)of 19-day-old chicken embryo,mainly heart,liver and spleen,lung,kidney,intestine,were sampled from same farm and examined with FRET-qPCR target for 23 S rRNA gene of Chlamydia spp.The detections of FRET-qPCR showed that 75%(75/100)laying hens from breed farm in Shaobo were positive for C.gallinacea.Meanwhile,semen samples of 28 rosters were negative.In the 294 eggs for hatching,the positivity of Chlamydia in shell swabs of them(97.6%,287/294)were higher than in egg albumen samples(7%,9/128)and yolk samples(5.4%,7/128).With FRET-PCR used in this study,we detected nucleic acids of C.gallinacea from 8 embryos(14.5%,8/55)and organ samples,including heart(9%,5/55),liver(5.5%,3/55),spleen(12.7%,7/55),lung(11%,6/55),kidney(14.5%,8/55)and intestine(7.3%,4/55).As far as we know,this is the first report that the C.gallinacea was transmitted through fecal-oral route horizontally in chickens.It assumed that C.gallinacea vertically transmit through the shell of egg into the embryo which will be verified with more experiments. |
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