Enzyme immunoassay of Chlamydia in birds.

Serum samples from 192 free-living birds (27 species) were tested for antibodies against Chlamydia using the enzyme-linked immunosorbent assay (ELISA); 97 (51%) were seropositive. The highest antibody prevalence was among pheasants (96%), ducks (88%), and blackbirds (86%). None of 41 starlings tested were seropositive. The serotesting of 42 confined pheasants indicated 100% exposure to the organism. The ELISA is a sensitive, rapid serologic method that can be of epidemiologic and diagnostic value for detecting exposure to Chlamydia. The ELISA could also be used for mass-screening of pet birds where chlamydiosis may be considered a potential public health hazard.

Evaluation of the fluorescent antibody test for diagnosis of paratuberculosis.

Results of indirect fluorescent-antibody microscopy did not differ significantly from complement-fixation test results in diagnosing paratuberculosis (Johne's disease) in cattle. Neither test had acceptable sensitivity or specificity for detecting subclinical cases.

Comparison of the enzyme-linked immunosorbent assay with other tests for brucellosis, using sera from experimentally infected heifers.

During an evaluation of H-38 Brucella melitensin vaccine, serum samples were collected from 24 Hereford-Angus heifers (nonvaccinated controls) before exposure and then 11 times between 12 and 102 days after exposure to Brucella abortus strain 2308. Antibody concentrations were determined by the enzyme-linked immunosorbent assay (ELISA) and by standard tube agglutination (STA), 2-mercaptoethanol agglutination (ME), microtitration complement-fixation (MCF), and automated complement-fixation (ACF) tests. The results were compared in terms of concordance, sensitivity, and specificity. Concordance between the ELISA and other tests were 100% (STA), 75.7% (ME), 97.8% (MCF), and 95.2% (ACF). On the 12th day after heifers were exposed, antibodies were detected in 18.2% of the infected heifers by the ELISA and in 11.1% with the STA test, in 0% with the ME test, in 33.3% with the MCF test, and in 44.4% with the ACF test. On the 25th day, ELISA and all serotests (except ME) detected antibodies in all infected heifers. All serum samples from the heifers before exposure were negative.

Enzyme immunoassay for surveillance of Q fever.

An enzyme-linked immunosorbent assay (ELISA) was developed to monitor antibodies against Coxiella burnetii among animal populations used in research and teaching facilities. Various antigenic components of C burnetii prepared from phase I and phase II whole cells and commercially available antigens were evaluated. A trichloroacetic acid extract was selected for routine use. There was a linear relationship between the transformed absorbance readings of the ELISA results and microagglutination (MA) titers. Comparison between positive or negative results of the MA test and ELISA gave 98.6% concordance. Using the MA test as the standard, ELISA results were 97.8% sensitive and 100% specific. The efficacy of ELISA was evaluated by testing ruminants with known histories of C burnetii infection. Antibody prevalence was 0 in 117 sheep with no history of C burnetii infection, 22% in 145 naturally infected sheep used for research, and 53% in 115 sheep used for vaccine field trials. Forty-eight percent of 120 dairy cows and 52% of 79 goats from endemically infected herds were seropositive. These results indicate that ELISA should be the test of choice for mass screening and surveillance of animals when Q fever is a suspected biohazard.

Epidemiologic study of toxoplasmosis on a sheep ranch.

An epidemiologic study was done on a ranch in northern California on a flock of ewes that had a history of abortions, mummified fetuses, weak or stillborn lambs, and failure to conceive. Of 56 ewes tested, 33 (59%) had serum agglutinating antibodies against Toxoplasma gondii, with an unusually high proportion of high titers. Over a 2-year-period, reproductive problems were higher (39% to 42%) among the seropositive ewes than among the seronegative ewes (9% to 33%). Of 89 sera received from persons and 7 species of animals on the ranch, 44 (49%) were found to be seropositive to T gondii, including seropositive members of a family of 6. The rancher's wife and teenage daughter, both of whom were involved with lambing, had serum titers exceeding 4,096. Other members of the family not involved with lambing were seronegative by the indirect hemagglutination test. The 2 infected persons are known to have come in contact with placentas, birth fluids, fetuses, and colostrums from these infected ewes.

Q fever (Coxiella burnetii) investigations in dairy cattle: persistence of antibodies after vaccination.

The immune response and persistence of antibodies were investigated in dairy cattle vaccinated with formalin-inactivated phase (ph) I Coxiella burnetii vaccine agglutinating antibody geometric mean titer (GMT) of 193.2 at 1 month after vaccination compared to a GMT of 2.0 for nonvaccinated calves. The agglutinating antibodies gradually decreased in vaccinated cattle, but the GMT remained approximately 4 times higher than that for the nonvaccinated group for at least 20 months. Results of serotests at 2 months after revaccination indicated a rapid increase in the GMT to 177.0 with agglutinating titers between 1:64 and 1:512.

Mass screening of cattle sera against 14 infectious disease agents, using an ELISA system for monitoring health in livestock.

Mass screening ELISA methods were developed for testing cattle serum for antibodies against 14 common livestock diseases simultaneously. The absorbance values were transformed to a %ELISA (spectrophotometric antibody end point) by a computer interfaced with a microplate reader. A histogram indicating a cutoff point and a report for the veterinarian also was generated. The computer program produced a print-out of the antibody profile for each animal tested, the antibody concentration against each disease, and a histogram (antibody profile) showing the prevalence of each disease in the herd. Serum samples were obtained from 1,953 cattle, including 880 dairy cattle from 10 herds and 1,073 beef cattle from 20 herds. These samples were obtained from June 1988 through June 1989. The highest antibody prevalence was against bluetongue virus. Of the 1,953 cattle tested, 1,223 (63%) were seropositive for bluetongue virus, including 502 (57%) of the dairy cattle and 721 (67%) beef cattle. Other antibody prevalences, in descending order, were: rotavirus (44%), Pasteurella spp (25%), Leptospira spp and Haemophilus spp (22%), Mycoplasma spp (18%), parainfluenza virus (17%), Campylobacter spp (16%), Anaplasma marginale (15%), bovine leukosis virus (13%), Brucella spp (8%), Mycobacterium paratuberculosis (8%), bovine viral diarrhea virus (3%), and infectious bovine rhinotracheitis virus (3%). Major differences in antibody prevalence between dairy and beef cattle were that only 4% of the dairy cattle were seropositive for A marginale, compared with 25% of the beef cattle, and conversely, 29% of the dairy cattle were seropositive for bovine leukosis virus, compared with 1% of the beef cattle.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of Coxiella burnetii (Q fever) and Toxoplasma gondii among dairy goats in California.

The prevalence of antibodies against Coxiella burnetii and Toxoplasma gondii, the causative agents of Q fever and toxoplasmosis, was examined in goats to determine the extent of the potential of goats to tansfer these infections to persons. Of 1,054 goats from 234 premises in California, 248 goats (24%) were seropositive for C burnetii and 246 (23%) were seropositive for T gondii. Of 29 dairy goats tested, 2 (7%) were found to be shedding the Q fever rickettsia in their milk; T gondii was not detected. Factors of sex, age, location, and herd size are discussed.

A field study of persistence of antibodies in California horses vaccinated against western, eastern, and Venezuelan equine encephalomyelitis.

As a result of the continuing threat of Venezuelan equine encephalomyelitis (VEE), a study was made to determine if revaccination against VEE (TC-83 vaccine) was feasible and if revaccination could be incorporated into other routine vaccination practices. Of the horses given annual vaccination with bivalent western equine encephalomyelitis (WEE) and eastern equine encephalomyelitis (EEE) vaccine, 57% retained detectable serum-neutralizing (SN) antiboyd titers for VEE 18 months after the initial VEE vaccination was given. Of horses with no record of WEE-EEE vacinnation, 100% retained detectable VEE SN antibody titers over the same period. The VEE geometric mean titer was 25 times greater for horses not previously vaccinated against WEE-EEE than for horses given annual WEE-EEE vaccination at the time of VEE vaccination. In horses vaccinated against VEE 18 months previously, the geometric mean titer increased from 4 to 70 at 48 days after the intitial WEE-EEE vaccination. This increase indicated that similar antigenic factors for VEE are possibly present in bivalent WEE-EEE vaccine. In horses previously vaccinated against WEE-EEE and VEE, the best SN antibody response to VEE revaccination occurred when VEE vaccine was given simultaneously with the bivalent WEE-EEE vaccine. Of 150 serum samples tested by both the SN and the hemagglutination-inhibiton tests, agreement between positive reactions at greater than or equal to 1:10 was 70% for VEE, 81% for EEE, and 87% for WEE.

Q fever (Coxiella burnetii) investigations in dairy cattle: challenge of immunity after vaccination.

The immunity of Holstein-Friesian dairy cows vaccinated against Coxiella burnetii was challenged with 4 X 10(8) infective guinea pig doses of viable rickettsiae. Cows that were vaccinated had normal full-term calves, whereas 2 nonvaccinated cows aborted late in pregnancy. Intrauterine infection of the fetus was indicated by recovery of the organism from tissues of the fetus. Coxiella burnetii was recovered from milk, colostrum, and placenta of vaccinated and nonvaccinated cows after challenge inoculation, but the rickettsiae recovered were as many as 1,000 times more numerous in nonvacinated cows.

Equine toxoplasmosis: a survey for antibodies to Toxoplasma gondii in horses.

A nationwide sample of horses was tested to determine the prevalence of toxoplasma antibodies in equine animals. Of 1,294 serum samples from horses tested by the microtitration indirect hemagglutin test, 20% were positive. Among the popular breeds of horses, the following antibody prevalences were found: Arabian, 19%; Paint, 22%; Quarter Horses, 13%; Thoroughbred, 24%; and Standardbred, 17%. The antibody prevalence increased from 2% in horses 1 year of age to 18% in 2-year-olds, and rose to 38% in horses 12 years of age. Significant differences were not evident by broad geographic locations across the United States. However, there were differences in prevalence according to premises where the horses were kept. On some ranches, there was no evidence of infection, whereas up to 67% of the horses on other premises were seropositive for toxoplasmosis.

Vaccination of dairy cattle against Q fever (Coxiella burneti): results of field trials.

A phase I formalin-inactivated Q fever vaccine, using the Nine Mile strain of the organism, was tested for its ability to prevent dairy cows from shedding Coxiella burnetti in their milk. More than 1,400 Holstein-Friesian dairy calves and heifers from 5 dairies were used in field trials lasting over a 3-year period. Vaccination of 476 calves resulted in a geometric mean antibody titer of 1:123.3 compared with 1:2.4 for 486 nonvaccinated calves. The milk samples from 163 vaccinated calves were tested by mouse inoculation after the cows commenced lactation and were placed in their respective milking herds. Of these vaccinated animals, only 2 cows (1%) from 1 herd were suspected shedders, but on subsequent testing gave negative results. Among 164 nonvaccinated (control) cows, 39 (24%) were shedding C burnetii in their milk; this figure corresponded to the prevalence (23%) of shedders in the general population of dairy cows in California. The results of the current field trials indicated that vaccination greatly reduced the shedding of the Q fever organism in the milk of dairy cows.

Q fever vaccination of sheep: challenge of immunity in ewes.

Adult ewes (17 months of age) were vaccinated against Coxiella burnetii, using a formalin-inactivated whole cell (WC) phase I Henzerling strain vaccine or a chloroform methanol residue (CMR) vaccine. Nineteen pregnant ewes were placed in 3 categories [(i) unvaccinated, (ii) WC vaccine, and (iii) CMR vaccine] and were challenge exposed at approximately the 100th day of gestation with 210,000 plaque-forming units of C burnetii inoculated subcutaneously. Shedding of rickettsiae was measurably reduced, but was not prevented in vaccinated groups, as shown by inoculating ewes' placental tissues, amniotic fluid, and colostrum into mice, as well as by histopathologic lesions of placental tissues. The rickettsiae were shed in the placenta, amniotic fluid, or colostrum in 6 nonvaccinated ewes. In comparison, rickettsiae were detected in placental inoculations from 2 of 6 ewes in the WC vaccine group and 1 of 6 in the CMR group. In contrast to those in the vaccinated ewes, placentitis, high concentrations of rickettsiae in microscopic preparations, and weak lambs were typical for the nonvaccinated ewes.

Toxoplasma antibodies among bobcats and other carnivores of norther California.

The prevalence of antibodies to Toxoplasma gondii was investigated among five species of wild carnivores in Norther Ccalifornia. The highest prevalence was among bobcats (Lynx rufus), with 15 of 21 tested being serologically positive. Other results included serological evidence of toxoplasmosis in two of seven raccoons (Procyon lotor), one of three badgers (taxidea taxus) and two of three coyotes (Canis latrans). Two gray foxes (Urocyon cinereoargenteus) were serologically negative. Oone badger with an indirect hemagglutination antibody titer of 1:8192 was found to harbor T. gondii in its brain tissues.

Toxoplasma gondii antibodies in free-living African mammals.

Twelve species of free-living African mammals from Kenya, Tanzania, Uganda and Zambia were tested for antibodies to Toxoplasma gondii using the indirect hemagglutination test. Of 157 animals sampled, 20 (13%) were seropositive. T. gondii antibodies were detected in Burchell's zebra, (Equus burchelli), hippopotamus (Hippopotamus amphibius), African elephant (Loxodonta africana), defassa waterbuck (Kobus defassa), lion (Panthera leo), and rock hyrax (Procavia capensis), The highest titers were found in elephants, two having titers of 1:4096 and one of 1:8192. These results are discussed in relation to the maintenance of T. gondii among African wildlife.

Evaluation of the hemagglutination test for epidemiologic studies of leptospiral antibodies in wild mammals.

Sera from 153 wild animals of 18 species were tested for antibodies against 12 serovars of Leptospira by the microscopic agglutination (MA) test. Seventy-five percent of the animals tested were seropositive against one or more of the 12 serovars used. The most commonly found serovars were pomona, autumnalis, pyrogenes, icterohaemorrhagiae, australis, and canicola. Of 62 carnivores representing 7 species, 55 (89%) were seropositive, as were 46 (60%) of 77 rodents from 9 species. Leptospira of the serovar copenhageni serogroup icterohaemorrhagiae were recovered from kidney tissues of a Norway rat (Rattus norvegicus). Of 443 wildlife sera tested by the indirect hemagglutination (IHA) test using cells sensitized with L. illini antigen, 47 (11%), mainly carnivores and deer, gave a heterophile reaction. Of the remaining 396 sera, 164 (41%) were seropositive for leptospirosis by the IHA test. To compare the IHA test with the MA test, 143 serum samples were tested by both methods. There was 84% concordance between the two tests.

Survey of Q-fever agglutinins in birds and small rodents in Northern California, 1975-76.

Serum samples from 15 species of rodents and 33 species of birds were tested for agglutinins against Coxiella burnetii by the microagglutination test. Of 759 rodents tested, 21 (3%) were seropositive. Antibody positive rodents included muskrats, Ondatra zebethica, (11%), Rattus spp. (10%), Beechey ground squirrels, Otospermophilus beecheyi, (6%), wood rats, Neotoma fuscipes, (5%), and Peromyscus spp. (2%). Of 583 birds tested, 118 (20%) were seropositive. This included white crowned sparrows, Zonotrichia leucophrys, gold crowned sparrows, Z. atricapilla, and English sparrows, Passer domesticus, (68% in the composite); coots, Fulica americana, (29%); blackbirds, Euphagus cyanocephalus, (33%); crows, Corvus brachyrhyncos, (29%); robins, Turdus migratorius, (16%); pigeons, Columba fasciata, (10%); and mallard ducks, Anas platyrhynchos, (7%). There was a tendency for the seropositive animals to have been collected in the vicinity of endemically infected livestock.

Prevalence of Toxoplasma gondii antibodies in wild and domestic animals in northern California.

Wild and domestic animals from 3 geographic-climatologic areas in northern California were tested for antibodies against Toxoplasma gondii. A total of 2,796 serum samples representing 37 species of wild mammals, 35 species of wild birds, and 5 species of domestic animals were tested by the indirect hemagglutination test. Of 1,174 wild mammal serums tested, 10.8% were positive, which compared with 14.7% of the 1,221 domestic mammal serums. Of 229 wild carnivores tested, 45% were seropositive, including 69% of 86 bobcats, 28% of 58 coyotes, 48% of 25 raccoons, 27% of 26 gray foxes, 22% of 32 striped skunks, a civet cat, and a mink. Serologic evidence of infection was found in 38% of 47 rural domestic cats, but none of the 7 dogs tested was seropositive. Of 160 murid rodents (rats and house mice) in rural habitats, 4% were seropositive, which compared with 2% of 399 cricetine rodents (mostly deer mice) collected from wilderness habitats. Seven percent of 56 wild Artiodactyla (deer and feral pigs) were seropositive, which compared with 15% of 1,048 domestic sheep tested. Of 401 birds tested, 3.5% had antibodies against T gondii. The highest prevalence of antibodies among birds was in crows (14%). Toxoplasma was isolated from 1 raven, by mouse inoculation. In general, the highest prevalence of seropositive carnivores, rodents, and sheep was in the coastal region below 100 ft elevation, where the weather is cool and damp for much of the year. In the central valley the highest prevalence among sheep was in areas under irrigation. The prevalence of antibodies was lowest in the mountain areas, where climatologic extremes prevail at various seasons of the year.

Serologic survey for certain zoonotic diseases in black bears in California.

Black bears (Ursus americanus) from 3 geographic areas of California were tested for antibodies against agents of 6 zoonotic diseases: toxoplasmosis (indirect hemagglutination), Q fever (microagglutination), trichinosis (latex particle agglutination), botulism (passive hemagglutination), leptospirosis (plate agglutination), and plague (enzyme-linked immunosorbent assay). Of 149 sera tested, 40 (27%) were positive for Toxoplasma gondii antibodies and 25 (17%) had antibodies against Coxiella burnetii. Of 141 bears tested for Trichinella spiralis, 18 (13%) were seropositive, and 19 (15%) of 125 tested had antibodies against the plague organism, Yersinia pestis. Only 2% (2 of 123 tested) had antibodies against Clostridium botulinum. Sera from 129 bears were tested against 4 pools of Leptospira interrogans representing 12 serovars, and 16% of the sera reacted with the pool containing the serovars australis, hyos, and mini georgia.

A survey for Toxoplasma gondii antibodies in deer and other wildlife on a sheep range.

Blood samples were obtained from native mammals and birds on a sheep range (Hopland Field Station) in northern California. Serums were tested for antibodies to Toxoplasma gondii by the indirect hemagglutination test. Of 382 deer that were tested from 1964 to 1973, 77 (20%) were seropositive for T gondii. Among 36 serums representing 6 species of wild carnivores (badgers, bobcats, coyotes, foxes, raccoons, and skunks), 18 (50%) were seropositive. All of the 5 bobcats tested were seropositive, with antibody titers ranging from 1:65,536. The testing of 175 serums from small wild mammals indicated antibody prevalence of 8% among jackrabbits, 6% among brush rabbits, and 2% among squirrels. None of the native mice tested was seropositive for T gondii. Of 120 native birds tested, 6 (5%) were seropositive. Of the resident domestic species of animals tested, antibodies were found in 1 of 7 domestic cats, 1 of 5 feral cats, 1 of 2 dogs, and 54 (13%) of 405 sheep.