David W. Dreesen

Antibody Response to Preexposure Human Diploid-Cell Rabies Vaccine Given Concurrently with Chloroquine

We conducted a randomized controlled trial to evaluate the antibody response of freshman veterinary students to intradermal human diploid-cell rabies vaccine administered concurrently with chloroquine, a drug frequently used for chemoprophylaxis against malaria. Fifty-one students who had not been vaccinated against rabies were enrolled: 26 received 300 mg of chloroquine base per week (the recommended dose for malaria prophylaxis); 25 did not receive chloroquine and served as controls. All subjects received 0.1 ml of rabies vaccine intradermally on days 0, 7, and 28. Chloroquine was administered weekly to the treatment group, beginning nine days before the first dose of vaccine and continuing until day 48. The mean rabies-neutralizing antibody titer for the chloroquine group was significantly lower than that for the control group on each day of testing--i.e., day 28 (P = 0.0094), day 49 (P = 0.0008), and day 105 (P = 0.0002)--although both groups had neutralizing antibody titers on days 49 and 105, according to the criteria of the Centers for Disease Control. The blood concentrations of chloroquine and desethylchloroquine (the major metabolite of chloroquine, which also has antimalarial properties) were negatively associated with log antibody titers. These results indicate that chloroquine taken in the dose recommended for malaria prophylaxis can reduce the antibody response to primary immunization with intradermal human diploid-cell rabies vaccine.

Prevalence of Salmonella enteritidis and other serovars in ovaries of layer hens at time of slaughter

Ovaries aseptically collected from commercial layer hens at time of slaughter were assayed for Salmonella as an indication of systemic infection of birds within a flock. Birds were randomly selected at the time of slaughter from 42 flocks from seven southeastern states and Pennsylvania. Ovaries were pooled, four per pool, mascerated, and Salmonella , isolates were recovered by conventional methods. Thirty-two of 42 flocks (76.2%) were positive at >10% infection rate based on sampling methods. Fifteen different serovars were detected in flocks. Salmonella heidelberg was the predominant serovar, representing 56.5% of the salmonellae detected. However, S. agona , S. oranienburg , S. mbandaka , S. kentucky , S. montevideo , S. london , S. typhimurium , S. infantis , S. schwarzenqrund , S. ohio , S. cerro , S. anatum , and Salmonella untypeable were also found. S. enteritidis , phage type 23 was recovered from only one (2.4%) of the flocks. Single and multiple serovar infections were found with up to five serovars recovered from a single flock. Twenty-one positive flocks (50%) were positive with a single Salmonella serovar; of these S. heidelberg represented 76.2%. An overall mean of 26.6% of the pooled ovary samples within each infected flock was positive for salmonellae, with an overall range of 0-100%. The significance of Salmonella serovars other than S. enteritidis found at the levels reported has yet to be determined.

Immune complex-like disease in 23 persons following a booster dose of rabies human diploid cell vaccine

Following a routine 0.1 ml booster dose of Merieux rabies human diploid cell vaccine (HDCV), administered intradermally, 23(10.2%) of 226 persons had signs and symptoms compatible with an immune complex-like disease. The disease had its onset from 3-13 days after the injection, lasted 1-5 days, and consisted primarily of urticaria (78.3%), macular rash (65.2%), angiooedema (39.1%), and arthralgia (17.4%). None of the cases were considered severe, and all recovered with no sequelae. There were significant differences in attack rates between men (78.3% of all cases) and women, and between those receiving vaccinations on different days. Similar reactions have been reported following intramuscular booster doses of HDCV. Since the Merieux HDCV is used worldwide, physicians administering HDCV must be aware of these adverse reactions and warn patients. Appropriate therapy should be instituted as warranted by severity of reactions.

Risk factors for systemic hypersensitivity reactions after booster vaccinations with human diploid cell rabies vaccine: A nationwide prospective study

To determine the incidence of and risk factors for adverse reactions following the boosters, we conducted a nationwide prospective study of persons receiving pre-exposure booster vaccination with human diploid cell rabies vaccine (HDCV). Persons who had previously received three pre-exposure doses of HDCV and whose rabies neutralizing antibody titres were < or = 1:5 were enrolled in the study if they stated that they intended to receive a booster. Of the 98 persons enrolled in the study, 40 (41%) were in risk groups for whom boosters are not recommended. Three (3%) of 98 developed generalized urticaria or wheezing within 1 day of receiving boosters and three others (3%) developed urticaria 6 to 14 days after the booster. No differences were found between individuals with reactions (either type) and those with no adverse reaction according to age, gender, occupation, history of previous allergies, or time since or route of primary vaccination. Reactions were somewhat more common among persons who received primary vaccinations by the intramuscular route (i.m.) and booster vaccinations by the intradermal route (i.d.) (3/15, 20%) or primary vaccinations i.d. and booster vaccinations i.m. (2/10, 20%), and somewhat less common among persons who received both these vaccinations i.d. (1/52, 2%) or i.m. (0/7). The number of persons who develop allergic reactions may be minimized by administering vaccinations only when vaccination is strictly indicated. The influence of the route of primary and booster vaccinations on the development of reactions deserves further study.

A global review of rabies vaccines for human use

Rabies is one of the oldest known diseases of mankind, yet it has been only slightly more than 100 years since Pasteur developed the first vaccine for post-exposure treatment. Since this first crude nerve tissue vaccine, numerous other rabies vaccines for human use have been developed and used with varying degrees of effectiveness and safety. When used appropriately, new cell culture vaccines provide nearly 100% protection with a high degree of safety: yet over 40,000 people world-wide die from rabies each year. Several pre- and post-exposure controlled vaccine trials and clinical studies have shown that the purified chick embryo cell (PCEC) vaccine, Rabipur, is as safe and effective as the rabies human diploid cell vaccine (HDCV), which is currently considered the gold standard. Additionally, PCEC vaccine does not result in immune-mediated hypersensitivity reactions following booster doses seen in about 6% of those receiving HDCV boosters following an initial series of HDCV.

Purified Chick Embryo Cell Culture Rabies Vaccine : interchangeability with Human Diploid Cell Culture Rabies Vaccine and comparison of one versus two-dose post-exposure booster regimen for previously immunized persons

The equivalence and interchangeability of Purified Chick Embryo Cell Culture Rabies Vaccine (PCECV) to Human Diploid Cell Culture Rabies Vaccine (HDCV) and the immunogenicity of a reduced post-exposure regimen with PCECV was investigated. Statistical analyses revealed no difference (P</=0.05) between the geometric mean titers (GMT) on day 49 of subjects that received PCECV or HDCV. In Year 2, subjects were boosted with one or two dose(s) of PCECV. No significant difference (P</=0.05) was detected between the GMT of the two groups on days 7 and 365 post-booster. Subjects that received HDCV initially developed an adequate anamnestic response to PCECV. On day 21 post-booster, the GMT of subjects that received two boosters was higher (151.6 IU/ml) than those that received one booster (120.9 IU/ml). However, this difference may not be clinically significant.

Human diploid cell rabies vaccine purified by zonal centrifugation: a controlled study of antibody response and side effects following primary and booster pre-exposure immunizations

Systemic allergic reactions following booster immunizations have complicated rabies pre-exposure prophylaxis with the human diploid cell rabies vaccine licensed in the US (conventional HDCV). We conducted two studies comparing an HDCV purified by zonal centrifugation to conventional HDCV. In a study of primary pre-exposure immunization, volunteers received one of four regimens: three 1.0-ml intramuscular (i.m.) or 0.1-ml intradermal (i.d.) doses of conventional or purified HDCV over 28 days. Although volunteers vaccinated i.m. had significantly greater rabies neutralizing antibody titres (VNA) 49 days, 91 days and 26 months after immunization began than volunteers vaccinated i.d. (p less than 0.005-p less than 0.05), there were no significant differences between vaccines. In a study of booster immunizations, 77 volunteers immunized with conventional HDCV 2 years earlier received a 0.1-ml i.d. booster with either conventional or purified HDCV. VNA was significantly greater with the conventional HDCV on days 7 and 28 after booster, but not on day 365. A moderate or severe reaction was reported by 5 (13%) of the 40 persons who received boosters with conventional HDCV, versus none of 37 who received the purified HDCV (p = 0.03). Purified HDCV appears to be preferable to conventional HDCV for booster vaccination.

Recovery of Aeromonas hydrophila from carcasses and processing water in a broiler processing operation

Aeromonas hydrophila , a potential pathogen associated with cases of human diarrhea, was enumerated using a rinse method on broiler carcasses and in processing water at selected locations in a commercial processing plant. A. hydrophila was detected on 98% of all carcasses tested, and 92% of all chill water samples; scald and rinse water samples were negative for this organism. Mean numbers on carcasses ranged for 28 CFU/ml of rinse fluid, detected immediately after the chiller, to 580 CFU/ml of rinse fluid at the post-evisceration stage. Water chilling and washing resulted in a significant reduction in A. hydrophila numbers on carcasses, while refrigerated storage (48 h) resulted in a significant increase. Data suggest that isolates recovered from carcasses may likely have been of intestinal origin and that the evisceration step was a probable cause of contamination. A. hydrophila levels on carcasses and processing waters showed no correlation to other bacteriological parameters which might be used in a process evaluation program.

The role of rodents and other wildlife in the epidemiology of swine toxoplasmosis.

Abstract Two swine production units and their contiguous wildlife populations were used for this study. These herds were located 7 miles apart in the major swine producing area of south central Georgia. Herd A had a Toxoplasma gondii antibody prevalence of 27.6% in all ages of swine sampled, with an increased incidence of 13.6% over a 5-month period. This herd was maintained under a semi-range condition. The swine in Herd B were maintained exclusively in concrete floored, enclosed buildings. This herd had a 0.85% T. gondii prevalence. Rodents and a few other wildlife and domestic species were trapped in or around both herds. These animals were examined for Toxoplasma antibodies using the same test procedure utilized for swine sera, the indirect immunofluorescent (IIF) test. Additionally, rodent tissues were homogenized and suspensions prepared for interperitoneal (I/P) inoculation into CF 1 laboratory mice. Rodents and wildlife species examined were: Mus musculus, Peromyscus leucopus, Rattus norvegicus, Sigmodon hispidus, Procyon lotor , and Didelphis marsupalis . Feral and domestic animals other than swine that also were tested for the presence of T. gondii antibodies included two cats, two horses, and a dog. The overall prevalence of T. gondii antibodies in all non-porcine species examined was 67% for those animals in and around the premises of Herd A, and 63% for those in and around Herd B. Toxoplasma infectivity of rodents whose tissues were processed and inoculated into laboratory mice correlated well with the results of the IIF test on the serum of these wild rodents. No tachyzoites of T. gondii were found in the peritoneal exudate of laboratory mice post I/P inoculation with wild rodent tissue, with one exception. While there was no significant difference in Toxoplasma infectivity in non-porcine species on these two premises, management practices appeared to be the determining factor in swine infection with T. gondii . Excluding wildlife precluded infection.

Bacteria on beef briskets and ground beef: correlation with slaughter volume and antemortem condemnation

Aerobic plate counts of 3,455 brisket and 1,370 ground beef samples were examined for association with slaughter volume in 547 U.S. beef slaughter establishments. In general, high-volume beef slaughter establishments control total aerobic bacteria counts on briskets and ground beef more effectively than small volume establishments. The lower Aerobic plate counts at high slaughter volumes may have resulted from uniformity of cattle slaughtered, specialization of labor, measures taken to prevent contamination, and effective decontamination of carcasses in high-volume slaughter establishments. In this study the prevalence of Salmonella contamination was found to be more closely associated with the health of animals brought to slaughter than with certain conditions in the slaughter establishments. The prevalence of contamination of brisket and ground beef samples with Salmonella was highest in calf slaughter establishments. Salmonella contamination on brisket samples increased as antemortem condemnation increased in establishments that slaughter calves. No association was found between Salmonella contamination and slaughter volume.