Studies on the response of ewes to live chlamydiae adapted to chicken embryos or tissue culture.

Ewes infected before gestation with chicken embryo or tissue culture adapted chlamydial strain B-577 were challenge inoculated with the homologous strain at four to 18 weeks of gestation. The ewes responsed with group specific complement fixing antibody titers of 1:8 to 1:256 by the second week after initial infection. A secondary antibody response in the surviving challenge inoculated ewes occurred at the time of lambing and reached titers of 1:32 to 1:256 by the second week after parturition. Group specific complement fixing antibodies did not appear to play a significant role in resistance to chlamydial infection. Ewes infected with the chicken embryo adapted strain B-577 excreted chlamydiae in their feces 60 days after inoculation. However, chlamydiae were not recovered from feces of ewes infected with the tissue culture adapted strain B-577. Placentas of ewes challenge inoculated by the intravenous route were consistently infected. Chlamydiae were recovered from placentas, some fetuses and lambs. In two instances when challenge inoculation was given by the intramuscular route, infection was detected only by the direct fluorescent antibody method.     

The effect of age on the response of sheep to vaccination with irradiated trichostrongylus colubriformis larvae

Vaccination with irradiated Trichostrongylus colubriformis larvae produced a high level of immunity, as judged by faecal egg counts and worm burdens following challenge with normal larvae, in nine of ten sheep aged 10 months. In lambs aged 3 months, vaccination was less effective. Some lambs developed partial immunity, but others did not respond.Serum levels of antibodies to T. colubriformis acetylcholinesterase reflected the extent of antigenic exposure rather than the degree of immunity acquired, and there was no evidence that the unresponsiveness of the lambs was due to a deficiency in antibody production.Unresponsiveness was not associated with the numbers of circulating lymphocytes, monocytes or granulocytes, or with the numbers of mast cells, eosinophils and neutrophils at the site of infection. However, there were many globule leucocytes in the intestinal mucosa of adult sheep which were resistant to challenge infection. On the other hand, few of these cells were found in vaccinated lambs which generally gave a poor response to challenge.     

Experimental conjunctival infection of lambs with a strain of Chlamydia psittaci isolated from the eyes of a sheep naturally affected with keratoconjunctivitis

Five ram-lambs were inoculated into the left conjunctival sac with the 15R isolate of Chlamydia psittaci, recovered from a sheep with keratoconjunctivitis. A sixth ram-lamb was kept in contact with them. The five lambs developed varying degrees of acute conjunctivitis and 14 days later C psittaci could be recovered from the inoculated eyes, from which Branhamella ovis was also isolated. The eyes were examined regularly for four months; C psittaci could not be re-isolated but the eyes developed varying degrees of follicular conjunctivitis. After four months the sheep were treated with corticosteroids in an attempt to reactivate a latent chlamydial infection but no chlamydiae could be isolated. Five months after the start of the experiment the six lambs were inoculated with 15R into the left conjunctival sacs. Acute conjunctivitis developed which was not as severe as after the first inoculation, but C psittaci could only be recovered from the left eyes of three sheep three days after inoculation. The eyes remained chronically affected by follicular conjunctivitis. Six months after the start of the experiment the left eyes were again inoculated with 15R; on this occasion acute conjunctivitis did not develop and chlamydiae could not be isolated. Chronic follicular conjunctivitis persisted until the experiment was terminated three months later.     

Clinical and immunological responses of ewes following vaccination with an experimental formalin-inactivated Chlamydia psittaci (ovis) vaccine and subsequent challenge with the live organism during pregnancy

The protection afforded by an experimental, killed, adjuvanted vaccine derived from the A22 strain of Chlamydia psittaci (ovis) against ovine enzootic abortion was studied. The vaccine was used undiluted (group A), at a dilution of 10(-3) (group B) and at a dilution of 10(-6) (group C). A fourth control group (group D) was inoculated with all components of the vaccine except the chlamydial antigen. A group of rams (group R) was also vaccinated with the chlamydial antigen diluted to 10(-3). Animals were challenged 70 days after mating with the A22 strain of C. psittaci (ovis) and were studied throughout pregnancy and the subsequent lambing period. Their cell-mediated immune responses were examined using a skin test and their humoral immune responses were studied using an ELISA. Tests for excretion of chlamydiae in their faeces and genital tract during pregnancy and after parturition and in the faeces of their lambs were made. The reproductive performance of the ewes was assessed by calculating the average weight of lambs produced per ewe in each group. The experimental vaccine protected the ewes in groups A and B against challenge with C. psittaci (ovis) as none showed clinical signs of OEA or excreted chlamydiae. The average weight of lambs produced per ewe in both groups was greater than 4 kg. Both groups seroconverted after vaccination but not all of them were positive to the skin test. The experimental vaccine at 10(-6) dilution of antigen did not protect the ewes as three of 10 ewes displayed clinical OEA and excreted chlamydiae in the products of parturition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urogenital infection and seminal excretion after inoculation of bulls and rams with chlamydiae.

Five mature rams and 4 bulls were inoculated parenterally with bovine or ovine chlamydial strains of type 1 and 2. One to 3 days later, all animals developed a chlamydemia lasting 4 to 8 days. Chlamydial agents were isolated from the semen near the end of the chlamydemic phase. All rams and 3 of 4 inoculated bulls excreted chlamydiae in the semen for 22 to 29 days. From 8 to 39 days after inoculation, selected rams or bulls were killed to test for chlamydial infection in the urogenital tract and other organs. Chlamydiae were isolated in developing chicken embryos from testis, epididymis, and accessory sex glands. Bulls examined 29 and 39 days after inoculation did not harbor chlamydiae. Chlamydiae were also not isolated from 3 control bulls which were from the same herd as the principal bulls. All inoculated bulls and rams had a group-specific chlamydial antibody response within 7 days. The titers reached maximal levels of 128 to 512 at 14 days after inoculation. Subsequently, the antibody titers decreased gradually. Seminal plasma collected at different times after animals were inoculated did not fix complement in the presence of chlamydial group antigen. The number of polymorphonuclear leukocytes in the semen increased during the experiment. The semen was grossly purulent in 2 rams inoculated with the type 2 chlamydial strain of polyarthritis.     

Field studies of the immunisation of lambs with drug-abbreviated infections of Trichostrongylus colubriformis and Ostertagia circumcincta

Fifty, 5–6 month-old lambs were randomly allocated to five equal groups. Three groups of lambs were immunised by three oxfendazole-abbreviated (artificial) infections of Trichostrongylus colubriformis and Ostertagia circutncincta. Group 1 was immunised with a high dose of larvae, Group 2 with a medium dose and Group 3 with a low dose. A fourth group was treated with oxfendazole only and a fifth group was not treated (control). All groups were grazed together on pasture naturally contaminated with nematode larvae. Immunisation significantly reduced the number of eggs per gram of faeces in all three groups, but the lowest faecal egg count was seen in Group 3 (immunised with the lowest number of larvae). Significantly better liveweight gains and wool weight were observed in Group 2 animals than in the control group. Of all anthelmintic-treated animals, only Group 1 lambs did not have a signscantly lower dag weight than controls.     

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.     

Experimental Chlamydia psittaci serotype 1 enteric infection in gnotobiotic piglets: Histopathological,immunohistochemical and microbiological findings

The enteric pathogenicity of the ovine C. psittaci serotype 1 isolate S26/3 was assessed using a litter of gnotobiotic piglets. In one group, eight piglets were inoculated at 3 days of age; at 10 days, two of these were re-inoculated. In a second group, six animals were mock-inoculated at 3 days of age as negative controls; subsequently, at 10 days, three of these piglets were inoculated with C. psittaci. The animals were observed for clinical signs, killed and necropsied sequentially between 4 and 17 days of age. At necropsy, specimens were collected for histopathology, immunohistochemistry and serology. Clinical manifestations consisted of sporadic slight softening of faeces observed between 8 and 12 days post inoculation (d.p.i.) in pigs inoculated at 3 days of age and between 4 and 6 d.p.i. in those inoculated at day 10. Histopathological changes were minimal and inconsistent and occurred almost exclusively in the small intestine in pigs of 15 days of age and older; they consisted of a slight shortening of villi, of a small number of tongue-shaped villi and of villous fusions. Immunohistochemistry revealed small numbers of chlamydial inclusions in the small intestinal enterocytes of only five pigs, all killed within 5 d.p.i. An ELISA run on faecal samples collected daily after inoculation from six of the pigs showed that chlamydial antigen was excreted in the faeces. In pigs inoculated at 3 days, chlamydial antigen was detected inconsistently before, and consistently after 9 d.p.i. Pigs inoculated at 10 days excreted antigen consistently after inoculation until the end of their observation period (8 d.p.i.). Infective chlamydiae were detected from the faeces of inoculated piglets using Vero cell cultures. Sera of all pigs were negative for anti-chlamydial antibodies using a complement fixation test. In conclusion, enteric pathogenicity of C. psittaci serotype 1 in a litter of gnotobiotic piglets proved minimal. The results, therefore, indicate that serotype 1 C. psittaci is not likely to cause enteric disease in conventionally reared pigs. Nevertheless, a potential role of swine in the epidemiology of this agent should be considered with regard to spread of Chlamydia to other species.     

Traumatic myositis ossificans in a dog

AIM: To determine the distribution of the three common Trichostrongylus spp. infecting sheep and their resistance status on farms throughout New Zealand, using PCR.

METHODS: Cultures were prepared from faecal samples from 70 farms while conducting faecal egg count reduction tests (FECRT) in lambs between 2010 and 2012. Trichostrongylus-type infective stage larvae (L3) were recovered from cultures, derived from untreated control and albendazole-, levamisole- and ivermectin-treated groups of lambs on each of the farms involved, and these were identified to species using PCR analysis of the second internal transcribed spacer region of ribosomal DNA. The species composition of the larvae present in cultures from the untreated control groups was examined across all farms to assess any potential differences in geographical distribution. In addition, the species composition of larvae cultured from the untreated and anthelmintic-treated lamb groups were compared to determine which species exhibited resistance to each of the anthelmintics used in the FECRT.

RESULTS: Of 67 farms with Trichostrongylus spp. present, 42 (63%) cultures from the untreated control groups contained all three Trichostrongylus spp. and no significant geographical patterns in their distribution were detected. Seven samples contained only one species. Irrespective of the anthelmintic efficacy levels, Trichostrongylus colubriformis dominated cultures prepared from lambs following treatment with albendazole (99.1 (95%CI?=?97?100)% of larvae) or levamisole (81.6 (95%CI?=?75.3?87.9)% of larvae), indicating the presence of widespread resistance in this species. In cultures prepared from levamisole-treated lambs, small numbers of T. axei larvae were also frequently present (5.4 (95% CI?=?1.3?12.4)% of larvae). Resistance to ivermectin was not found in any of the three Trichostrongylus spp. after PCR identification. Although larvae were identified, based on length, as being Trichostrongylus spp., for 24 of the 48 samples cultured following treatment with ivermectin, 100% of the larvae present were identified as Teladorsagia circumcincta.

CONCLUSIONS: As in previous surveys, all three Trichostrongylus spp. were common throughout New Zealand and no geographical patterns were detected in the current study. On all farms where resistance to albendazole and/or levamisole was indicated (i.e. efficacy <95%), the species identified as being resistant was T. colubriformis. Even where efficacies were >95%, T. colubriformis still tended to dominate in post-treatment cultures. While this could reflect a lower susceptibility of T. colubriformis to these anthelmintics, it seems more likely to indicate the presence of resistant genotypes in these populations. Similarly, T. axei also tended to be present after treatment with levamisole, which likely reflects a known lower susceptibility of this species to these anthelmintics.     

The protection of lambs from eperythrozoon infection while suckling Eperythrozoon ovis carrier ewes

When lambs born to and suckling Eperythrozoon ovis carrier ewes were inoculated with heparinised blood containing large numbers of E. ovis organisms, the lambs were either sterilised of the infection or patent infection was suppressed till the lambs were weaned. In vitro infection, transplacental transfer of antibodies or soluble antigens could not be demonstrated.     

Strongyle infections of small ruminants in Nigeria

A survey of strongyle infections was conducted in sheep and goats reared in a traditional e extensive husbandry system in two ecological zones if Nigeria. One zone had a seasonal pattern of infection. The majority of animals had faecal worm parasite egg counts of below 500 eggs per gram. Kids, and lambs younger than 3 months did not carry strongyle worm burdens, and the highest infection rate was found in the 7–12 month age group. A high proportion of small ruminants shed strongyle eggs during the postparturient period.The helminth species found by the use of larval culture techniques on the faeces were: Haemonchus contortus, Trichostrongylus colubriformis and Oesophagostonum columbianum. Adults of the same species were found in the few animals necropsied. The significance of the findings is discussed.     

Inhibition of the development of Trichostrongylus spp. as third stage larvae in sheep

In non-lactating Frisian ewes slaughtered in September and November 1975 and in ewes slaughtered in March/April 1976 at lambing, the majority of Trichostrongylus axei, T. vitrinus and T. colubriformis found were inhibited third stage larvae (L₃). However, some larvae at various stages of development were found in the animals slaughtered at lambing. In contrast, in lactating ewes slaughtered 6 weeks after lambing in April 1976, almost all Trichostrongylus spp. appeared to be adults. All ewes grazed a pasture heavily contaminated with gastro-intestinal nematodes from June 1975 until at least 2 weeks before necropsy.In lambs on the pasture from April or June 1975, and slaughtered in September and November 1975 and March 1976 after at least 2 weeks of isolation, only small proportions of the Trichostrongylus spp. populations appeared to be L₃. Similar results were obtained from tracer lambs kept at pasture from August 1975 to March 1976. The implications of these findings are discussed.     

Recurrence of Chlamydia suis infection in pigs after short-term antimicrobial treatment

The effect of short-term antimicrobial treatment on natural excretion of Chlamydia suis in rectal swabs and C. suis and Chlamydophila psittaci in nasal swabs was investigated in 47 clinically normal piglets by quantitative real-time PCR. Pigs were treated IM with 4 mg/kg enrofloxacin for 5 days (n = 22) or 2.5 mg/kg enrofloxacin for 3 days followed by 100 mg/mL tiamulin (n = 25). Antimicrobial treatment reduced the number of pigs positive for chlamydiae and the quantity of chlamydial DNA in positive swabs for a few days, but chlamydial excretion recurred in both groups. Short-term antimicrobial treatment at dosages recommended for treatment of other bacterial infections in pig herds was not effective in eliminating naturally occurring subclinical chlamydial infection in pigs.     

Immunizing potential of various stages of Taenia ovis eggs injected subcutaneously into neonatal or sixteen-week-old lambs

When viable eggs of Taenia ovis were given orally to 1-week-old lambs, infection occurred only in those lambs that had been deprived of colostrum. When viable eggs were injected subcutaneously into 1-week-old lambs, no larvae developed at the injection site, and no resistance was stimulated against an oral challenge of T. ovis eggs given 11 weeks later. However, when eggs, oncospheres or developing cysticerci were subcutaneously injected into 16-week-old lambs, all grew at the injection site and stimulated a high degree of immunity to oral infection. Colostrum-derived antibodies against T. ovis apparently suppressed the immunizing potential of T. ovis eggs injected subcutaneously into neonatal lambs.     

Infection of specific-pathogen-free lambs with parainfluenza virus type 3, Pasteurella haemolytica and Mycoplasma ovipneumoniae

Groups of specific-pathogen-free lambs were inoculated with combinations of parainfluenza virus type 3 (PI₃), Pasteurella haemolytica (P.h.) and Mycoplasma ovipneumoniae ( (M.o.). Acute, necrotising bronchopneumonia developed in 8/9 lambs inoculated with PI₃ followed by P.h. whereas only 1/5 lambs inoculated with PI₃ followed by a combination of M.o. and P.h. developed a pneumonic lesion. When M.o. was inoculated 29 days before PI₃ and P.h., pneumonia developed in 3/4 lambs but M.o. was not reisolated from any of the lungs. Pneumonia was observed in 1/5 lambs inoculated with P.h. alone and in 1/5 inoculated with M.o. plus P.h. In addition, one lamb in the latter group died of acute septicaemic pasteurellosis. None of the lambs inoculated with M.o. alone, PI₃ alone or PI₃ followed by M.o. had any gross or microscopic evidence of pneumonia although the virus alone, or in combination, did produce minor pulmonary lesions.These data suggest that M.o. is not an important primary or secondary lung pathogen.     

Histopathological,histochemical and immunohistochemical findings of the small intestine in goats naturally infected by Trichostrongylus colubriformis

Gastrointestinal (GI) strongyle infection remains one of the main constraints to goat production worldwide. Samples of small intestine from 15 Syrian goats naturally infected with Trichostrongylus colubriformis were examined by routine histology, histochemistry and immunohistochemistry to describe the histological changes and the phenotypes of inflammatory cellular components of the mucosa. Results indicated that the immune response to infection by T. colubriformis was characterized by an increased rate of the severity of the histologic lesions, an increase rate of T cell lymphocytes recruitment to the intestinal mucosa and quantitative and qualitative changes in the histochemical composition of mucin in goblet cells.     

Tick-Borne Fever in Lambs of Different Ages

Four groups of lambs aged 1 week, 4 weeks, 1/2 year and 1 year old respectively were inoculated with Ehrlichia phagocytophila infected blood. Clinical signs, temperature reactions, haematological changes and parasitaemia were more moderate in lambs inoculated with E. phagocytophila at the age of 1 week than those recorded in the older animals. The clinical response to tick-borne fever (TBF) appears to be more severe with increasing age of the lambs. The lymphocyte reactivity to mitogens was reduced in the TBF infected lambs, and was most pronounced in lambs in the 3 older age groups.     

Experimental infection of pregnant ewes with enteric and abortion-source Chlamydophila abortus

Two groups of pregnant ewes were experimentally infected oronasally in midpregnancy. A faecal and an abortion-source isolate of Chlamydophila abortus were used. They were derived from a healthy ewe from a flock with no history of abortion, and from an aborted foetus in a farm with enzootic abortion. As assessed by modified Ziehl-Neelsen (MZN) staining, egg culture, antigen ELISA, the Clearview test and immunohistochemistry, inoculation resulted in placental and/or foetal infection in all ewes. Histopathology revealed placentitis in two and four ewes inoculated with the enteric or abortion-source isolate, respectively, in addition, these samples were immunohistochemically positive for chlamydial antigen. All six ewes infected with the enteric isolate and five of seven ewes infected with the abortion-source isolate showed evidence for a serological response by an indirect ELISA or CFT. Neither chlamydiae nor lesions were detected in the placentae and lambs of the uninfected control ewes, which remained seronegative. Our results suggest that enteric C. abortus can be associated with placental and foetal lesions in sheep.     

Dietary impacts on the resistance of Merino lambs to Trichostrongylus colubriformis

AIM: To evaluate and compare the effects of a variety of diets on the resistance of young, lightweight Merino lambs to repeated low-dose infections of Trichostrongylus colubriformis.

METHODS: Ninety-six 12-week-old lambs were fed balanced or unbalanced diets, and given primary (at 19 weeks of age) or both primary (at 12 weeks) and secondary (at 19 weeks) infections of T. colubriformis. Suboptimal diets were low in total intake, rumen undegradable protein, total protein, readily available carbohydrate or minerals, or supplemented with cod liver oil. Liveweight was monitored fortnightly, protection was assessed from worm counts at the end of the study (25 weeks) and faecal nematode egg counts (FEC) conducted weekly, and mast-cell response assessed at the conclusion of the study from concentration of mast-cell protease in the jejunum. Concentrations of glucose in plasma were measured at 21 weeks.

RESULTS: Diets unbalanced for total protein, readily available carbohydrate, Mo or cod liver oil each increased the worm counts after 6 weeks of secondary infection (at 25 weeks of age) and FEC during secondary infection. Low intake of a highnutrient diet restricted liveweight gain but did not affect the development of resistance, as indicated by worm counts and FEC. Defi ciency of available carbohydrate resulted in reduced liveweight gain and reduced concentration of glucose in plasma. There was a reduction in jejunal mast-cell protease concentration in sheep fed unbalanced rations.

CONCLUSIONS: The parasitology results and reduction in the concentration of jejunal mast-cell protease observed in sheep fed unbalanced rations suggest that the nutrient defi ciencies and the fi sh-oil supplement may have acted via inhibition or retardation of the host's acquired immune response. Diets unbalanced for a range of components adversely affected the acquired protective response to T. colubriformis to a similar extent and appeared to involve a similar mechanism as each other. The quality of the diet was more important than quantity for the development of resistance, and soluble carbohydrate was an essential component.     

Immunization of neonatal lambs against the larvae of Taenia hydatigena, using viable eggs followed by chemotherapy

The subcutaneous injection of viable eggs of Taenia hydatigena into neonatal lambs induced 100% protection against the development of viable T. hydatigena larvae from an oral challenge. However, contrary to some published results, no protection was induced against a simultaneous infection with eggs of T. ovis and Echinococcus granulosus.The short-acting partial resistance to oral infection with T. hydatigena eggs, transferred from infected ewes to their lambs, was not enhanced by hyperimmunization of the ewe. In the lamb, this resistance did not interfere with the development of subcutaneously injected T. hydatigena eggs into immature larvae, or with the consequent induction of resistance to an oral challenge with T. hydatigena eggs. The immunizing lesion regressed rapidly after treatment of lambs with Mebendazole, and after 6 months the lesions were negligible in both treated and untreated lambs.