Conjunctival vaccination of young goats with Brucella melitensis strain Rev 1.

Three groups each of 15 four-month old female kids were vaccinated with Brucella melitensis strain Rev 1 either conjunctivally (1.1 x 10(7) or 1.1 x 10(9) CFU) or subcutaneously (1.1 x 10(9) CFU). One group of 15 kids remained unvaccinated as control. All kids were mated when 9.5 month old. Three months later, they were challenged conjunctivally with B melitensis strain H38 at a dose of 5.1 x 10(6) CFU. Blood samples collected before vaccination and throughout the experiment were subjected to Rose Bengal (RBPT) and Complement Fixation (CFT) tests. Allergy was tested both after vaccination and after challenge. Milk, uterine discharge as well as tissues from aborted foetuses and dead kids and from goats slaughtered 4-6 weeks after abortion or full-term kidding, were cultured on Farrell's medium. A serological response was shown in most kids vaccinated conjunctivally. However, 4 months after vaccination with either 1.1 x 10(7) or 1.1 x 10(9) CFU Rev 1, all animals were negative whereas some positive RBPT or CFT titres were still observed after the classical subcutaneous vaccination. There were more allergic reactions among subcutaneously than conjunctivaly vaccinated animals, but sensitization was shown long-lasting in all vaccinated groups, excluding allergic testing as a screening method in vaccinated flocks. Against a challenge which led all controls to abort, conjunctival vaccination was slightly better with 1.1 x 10(9) than with 1.1 x 10(7) CFU and almost as effective than that given by the subcutaneous one. These differences however were not statistically significant. These results quite agree with those previously recorded for ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Vaccination with a Listeria strain of reduced virulence against experimental Listeria abortion in goats.

A live Listeria monocytogenes strain of reduced virulence, strain Aer, obtained by three successive mutations in regard to streptomycin and erythromycin, was used as vaccine on goats in two successive experiments. Animals were vaccinated either once or twice by subcutaneous route with doses varying from 6 x 10(8) to 1.5 x 10(10) CFU. No side effect was observed, except in one goat, vaccinated as pregnant, that aborted and from which the vaccinal strain was reisolated. The goats were challenged by subcutaneous route with 5 x 10(8) CFU L monocytogenes virulent strain ATCC 19115 at 95-100 days of pregnancy. Thirteen out of 23 controls (56.5%) and 11 out of 24 once vaccinated goats (45.8%) aborted whereas only 5 out of 22 (22.7%) twice vaccinated goats aborted. Significant protection against a severe challenge can thus be afforded by vaccination and recall with the live strain L monocytogenes Aer.

Some aspects of experimental bovine brucellosis.

In the course of eight successive Brucella abortus experiments, 394 cows were followed by clinical, serological and bacteriological examinations. Cultures were made from vaginal swabs and colostrum at delivery and from 10 pools of lymph nodes or organs sampled at slaughter, about 6 weeks after calving. From these cows, 346 had been experimentally challenged with 1.5 X 10(7) B abortus strain 544 via the conjunctiva, 3 congenitally infected and 45 bought from known naturally infected herds. Males were more numerous (64%) in aborted foetuses and less numerous (34%) in premature live calves than females, the sex ratio being normal in calves born at term. Recovery of Brucella infection occurred between calving and slaughter in 13/230 cows (5.7%). It appeared that localization, spread and level of infection in different lymph nodes and organs, duration and outcome of pregnancy, and agglutination titers were strongly correlated. Comparisons between experimentally and naturally infected cows evidenced the fact that both types of infection were very similar. Confidence for field application of experimental results was thus reinforced.

Selection and characterization of a Listeria monocytogenes vaccinal strain of reduced virulence for mice.

In an attempt to reproduce resistance to Listeria monocytogenes induced by primo-infection, a vaccinal strain of low virulence capable of affording a good immunity was looked for. After a double mutation in regard to streptomycin, i.e. dependence then reversion to independence, nine strains were obtained from a Listeria monocytogenes field strain of low virulence. In addition, five of these reverse strains were made resistant to erythromycin. Measure of virulence of the resulting 14 strains was performed on mice by spleen counts three days after subcutaneous inoculation of 10(5) bacteria. A general decrease of virulence after the mutations was observed. Immunogenicity was estimated by spleen counts, three days after a challenge with parent strain on mice vaccinated one month previously with 10(6) organisms of each strain. A strain, resistant to erythromycin, was selected as potential vaccine, as having good immunogenicity, sufficiently reduced virulence, good growth ability and evident marker. This strain was shown resistant to 16 micrograms/ml of streptomycin and to 1000 micrograms/ml of erythromycin when respective values for parent strain were 4 micrograms/ml and 0.25 microgram/ml. Its metabolic activity in regard to glucids did not differ from that of parent strain but requirements in aminoacids increased at each step of the mutations leading from parent to selected strain. These characters were recognized as stable after two independent series of 10 passages on mice.

Vaccination against Listeria infection in mice with a mutant strain of reduced virulence.

Killed Listeria monocytogenes (L.m.) or living Listeria innocua, being unable to afford noticeable immunity against L.m. challenge in mice, the efficacy of a living strain of L.m. of reduced virulence was studied. This strain was obtained from a field strain of low virulence by successive mutations for streptomycin dependence, reversion to independence and resistance to erythromycin. Its protective immunity was checked in mice against IV, SC and intra-gastric challenges. Vaccinated mice were protected against a IV challenge, lethal for controls, and they were rid of infection in a much shorter time than controls after SC or intra-gastric challenges. They were also protected against abortion when the challenge was done by SC, but not by IV route. The level of immunity was shown to be dose-dependent. Appearing very early after vaccination, immunity remained stable for at least four months, then decreased slowly afterwards, but could be restored and even enhanced by a recall. The protection was equally effective against L.m. serovars 1 or 4 challenges.

Vaccination of ewes by a single conjunctival administration of Brucella melitensis Rev. 1 vaccine.

In a lot of 99 ewes, the efficacy of a single vaccination by the conjunctival route (VC) with either 1.4 X 10(8) or 1.4 X 10(9) CFU Brucella melitensis Rev. 1 was compared with that of normal subcutaneous (SC) vaccination with 1.6 X 10(9) CFU. The ewes were challenged seven months after vaccination, when 85 days pregnant, with 5 X 10(7) CFU Brucella melitensis strain H38 administered by conjunctival route. Complement fixation, Rose Bengal and allergic tests were performed at intervals between vaccination and slaughter, and clinical and bacteriological examinations between challenge and slaughter, six weeks after lambing. After VC vaccination, few animals showed Brucella antibodies whatever the dose, and all were seronegative as early as four months after vaccination whereas a few SC vaccinated individuals were still seropositive at ten months. There were more allergic reactions among SC than VC animals, but sensitization was shown to be long-lasting in all vaccinated groups, whatever the administration route of the vaccine. VC vaccination with 10(9) CFU appeared to afford slightly greater protection than that with 10(8) CFU, and slightly lower protection than that induced by SC vaccination, but differences were not statistically significant. It is suggested that conjunctival vaccination with 10(9) CFU Rev. 1 would induce a good level of protection against Brucella melitensis infection and allow test and slaughter procedures as early as four months after vaccination.

[Biological control of the brucellin INRA in sensitized guinea pigs: a guide for the statistical analysis of results]. / Contröle biologique de la brucelline INRA sur cobayes sensibilisés: guide pour l'analyse statistique des résultats.

Brucellin INRA is a new allergen used for the screening of brucellosis. It shows, by a delayed-type skin hypersensitivity reaction, the sensitization induced in animals by a brucella infection. The biological potency of each batch must be compared to that of a standard allergen. The use of guinea-pigs necessary for this quality control and the statistical analysis of the results are described and discussed. The aim of this paper is to provide the end-user with a simple and accurate method, and to alert him to the difficulties and limits of such a test.

[Listeria strains isolated from sick animals and consumed silage]. / Etude des souches de listeria isolées d'animaux malades et de l'ensilage consommé.

Forty-eight strains of listeria isolated from sick animals (27 goats, 19 sheep, 2 cows) from 33 farms, and 40 isolated from the silage eaten by these animals were studied. Listeria were isolated more frequently from poor quality silages than from those of good quality, although they were found in 11 out of 31 excellent silages with a pH value comprised between 3.6 and 4. The 88 strains were characterized by biochemical and serological examinations, phage typing and measurement of their virulence. They showed a wide variety of characteristics and in only one case, three strains with the same characteristics were isolated one from a dead ewe with symptoms of encephalitis and the two others from the silage it had eaten. In four flocks, identical strains were found in several animals from each farm, but in five other flocks, strains isolated from animals were different. The listeria of the silage may be the direct cause of the disease, but the isolation of strain with different characteristics from animals of the same flock led us to think that other causes might favour the infection. So, it seems difficult to control the disease only by enhancement of the quality of the silage.

[Effect of routes and doses of Salmonella abortus ovis inoculation on the abortive effect and serologic response of ewes]. / Influence des voies et doses d'inoculation avec Salmonella abortus ovis sur l'effet abortif et la réponse sérologique des brebis.

Three successive experiments using a restricted number of Préalpes X Lacaune ewes were designed to form a procedure allowing the reproduction of an abortive infection with Salmonella abortus ovis. Effects of inoculations at mid-gestation were estimated by the duration of gestation, bacteriological excretion at lambing and evolutions of rectal temperatures and of serological antibodies. Serological responses were revealed with four tests: O or H agglutination tests in tubes, H agglutination or complement fixation tests in microtechnics. Intravenous inoculations of 10(9) salmonella induced lethal septicaemia. Intragastric inoculations of 10(7), 10(8), 10(9) or 10(10) salmonella did not produce effects related to inoculated doses; in particular the only abortion obtained in this way occurred after inoculation of 10(7) salmonella. Subcutaneous inoculation of 10(6) to 10(10) salmonella induced serological, bacteriological and clinical responses related to the inoculated doses: ewes with at least two febrile phases during the 20 days post-inoculation aborted, including two ewes not excreting salmonella at lambing. After intragastric or subcutaneous inoculation, and with the four serological tests, the initial raising of titers was followed by an early and rapid decrease, without a new rise round about the time of abortion; no salmonella was isolated from ewes autopsied three to six months after inoculation. It appeared that the subcutaneous inoculation of 10(10) S. abortus ovis viable to ewes at mid-gestation was able to frequently induce a sublethal but abortive infection.

Efficacy of Brucella melitensis Rev. 1 vaccine against Brucella ovis infection in rams.

The efficacy of Brucella melitensis strain Rev. 1 vaccine against a Brucella ovis experimental infection was judged on 30 rams, 15 of which had received 8.5 X 10(8) Rev. 1 at the age of 4 months. All were challenged 9 months later by conjunctival route with 5 X 10(8) B. ovis. The 30 rams were killed three months after challenge and were autopsied. Genital and other organs and lymph-nodes were searched for B. ovis. Only a few organs and lymph-nodes of three vaccinated rams shed B. ovis, contrary to controls which were all heavily infected. The distribution of infection indicated that the most frequently infected organs are the vesicular glands which, more than epididymes, seem to be the target organs of the infection. These results show that immunization with strain Rev. 1 is very effective against B. ovis infection. It is recommended to vaccinate rams of four to six months in an area where B. ovis or B. melitensis infection, or both, are prevalent.

Comparison between subcutaneous and conjunctival route of vaccination with Rev. 1 strain against Brucella melitensis infection in ewes.

In areas where the prevalence of Brucella melitensis infection in sheep is high, control of the disease cannot be led without the help of vaccination. The use of Brucella melitensis strain Rev. 1 vaccine affords a very good protection. The drawback is that this vaccine, giving rise to long-lasting antibody titers, may disturb serological screening when a return is made to a test and slaughter policy, after several years of vaccination. There is a great need for another mode of vaccination which would avoid this disadvantage. In this experiment, the potency of a vaccination by conjunctival route with 1.4 X 10(8) Rev. 1, plus a recall of 2.9 X 10(8) six months later, was compared with that of the normal subcutaneous vaccination with 1.4 or 2.7 X 10(9) Rev. 1. The vaccination by conjunctival route afforded a somewhat better protection than the subcutaneous one, and with a shorter serological response. It may be possible that a single conjunctival vaccination, avoiding the difficulties of vaccinating twice in ovine flocks and giving few antibodies, could also afford a good protection. Research in progress should include investigation of this point.

Congenital brucellosis in cattle associated with localisation in a hygroma.

A heifer born to a cow experimentally infected with Brucella abortus strain 544 and reared in isolation from its birth was found infected. Antibodies appeared when it was 10 months old. The heifer calved normally. Brucella abortus of the same characteristics as strain 544 was recovered from a hygroma and from lymph nodes and udder. Five heifers out of 55 (about 10 per cent) born to infected dams and reared in isolation from their birth were found to be infected.

[Allergic diagnosis of bovine brucellosis. 2. Use of the allergic test in infected herds (author's transl)]. / Diagnostic allergique de la brucellose bovine. 2. Utilisation du test allergique dans les troupeaux infectés.

Four hundred and eighty-one cows, in 27 herds, were injected intradermally with a brucella purified protein allergen in order to study the value of the skin test in the diagnosis of bovine brucellosis. The serology was done on the serum or plasma from 444 of these cows. Two hundred and nine cows showed an allergic reaction and 174 were positive in serology. One hundred and twenty-three were simultaneously positive to both tests, 52 were positive in serology but did not show any allergic reaction and 66 showed an allergic reaction but were negative in serology. In general, brucellosis was certainly detected at the herd level with this test. In newly-infected herds, the skin test gives a more complete and earlier result than serological tests. The use of the skin test is recommended as a supplemental test when unknown animals are to be introduced in non-infected herds, to improve the detection of contaminated animals in newly-infected herds and to solve the case of problem herds.