Difference In Prevalence Of Antibodies Research Articles

Prevalence of SARS-CoV-2 antibodies during phased access to vaccination: results from a population-based survey in New York City, September 2020-March 2021.

Repeated serosurveys are an important tool for understanding trends in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. During 1 September 2020-20 March 2021, the NYC Health Department conducted a population-based SARS-CoV-2 antibody prevalence survey of 2096 NYC adults who either provided a blood specimen or self-reported the results of a previous antibody test. The serosurvey, the second in a series of surveys conducted by the NYC Health Department, aimed to estimate SARS-CoV-2 antibody prevalence across the city and for different groups at higher risk for adverse health outcomes. Weighted citywide prevalence was 23.5% overall (95% confidence interval (CI) 20.1-27.4) and increased from 19.2% (95% CI 14.7-24.6) before coronavirus disease 2019 vaccines were available to 31.3% (95% CI 24.5-39.0) during the early phases of vaccine roll-out. We found no differences in antibody prevalence by age, race/ethnicity, borough, education, marital status, sex, health insurance coverage, self-reported general health or neighbourhood poverty. These results show an overall increase in population-level seropositivity in NYC following the introduction of SARS-CoV-2 vaccines and highlight the importance of repeated serosurveys in understanding the pandemic's progression.

ANTIBODY PREVALENCE TO AFRICAN SWINE FEVER VIRUS, MYCOBACTERIUM BOVIS, FOOT-AND-MOUTH DISEASE VIRUS, RIFT VALLEY FEVER VIRUS, INFLUENZA A VIRUS, AND BRUCELLA AND LEPTOSPIRA SPP. IN FREE-RANGING WARTHOG (PHACOCHOERUS AFRICANUS) POPULATIONS IN SOUTH AFRICA.

The warthog (Phacochoerus africanus) can be used as a model for investigating disease transmission at the human, wildlife, and livestock interface. An omnivore and scavenger, a warthog moves freely between natural ecotypes, farmland, and human communities and is susceptible to diseases of zoonotic, agricultural, and conservation concern. A retrospective study using 100 individual serum samples collected from May 1999 to August 2016 was performed to determine antibody prevalence to seven pathogens in warthogs from five locations in northeastern South Africa. Higher prevalence of antibodies to African swine fever virus and Mycobacterium bovis were detected in warthogs from the Greater Kruger National Park ecosystem in comparison to lower prevalence of antibodies to M. bovis and no antibodies to African swine fever virus in warthogs from uMhkuze Game Reserve. Low prevalence of antibodies to foot-and-mouth disease virus, Rift Valley fever virus, and influenza A virus was detected in all locations, and no antibodies against Brucella and Leptospira spp. were detected. No statistically significant difference in antibody prevalence was found between sexes for any disease. At the univariate analysis, M. bovis seropositivity was significantly different among age categories, with 49% (35/71) of adults found positive versus 29% (4/14) of juveniles and 9% (1/11) of sub-adults (Fisher's exact test, P=0.020), and between the sampling locations (Fisher's exact test, P=0.001). The multivariate model results indicated that juvenile warthogs had lower odds of testing positive to M. bovis antibodies than adults (juveniles' odds ratio [OR]=0.17, 95% confidence interval [CI]: 0.02-1.0), although this result was not statistically significant at the 5% level (P=0.052). For warthogs sampled at Satara Buffalo Camp, the odds (OR=0.22, 95% CI: 0.035-0.96) of being M. bovis antibody positive were significantly lower (P=0.043) than for warthogs sampled at Skukuza. Of particular interest in this study was the detection of warthogs seropositive for influenza A virus.

Prevalence of serum anti-neuronal autoantibodies in patients admitted to acute psychiatric care.

Autoimmune encephalitis associated with anti-neuronal antibodies may be challenging to distinguish from primary psychiatric disorders. The significance of anti-neuronal antibodies in psychiatric patients without clear evidence of autoimmune encephalitis is unknown. We investigated the serum prevalence of six anti-neuronal autoantibodies in a cohort of unselected patients admitted to acute psychiatric care. Serum was drawn from 925 patients admitted to acute psychiatric in-patient care. Psychiatric diagnoses were set according to International Classification of Diseases (ICD)-10 criteria. Antibody analysis was performed with an indirect immunofluorescence test for N-methyl d-aspartate receptor (NMDAR) antibodies and five other anti-neuronal autoantibodies of the immunoglobulin (Ig) classes IgA, IgG and IgM isotype. Anti-neuronal autoantibodies were found in 11.6% of patients: NMDAR antibodies in 7.6%, contactin-associated protein-like 2 (CASPR2) antibodies in 2.5%, glutamic acid decarboxylase-65 (GAD65) antibodies in 1.9%, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antibodies in 0.1%. Leucine-rich glioma-inactivated protein-1 (LGI1) and γ-aminobutyric acid B (GABAB) receptor antibodies were not detected. NMDAR antibodies of class IgG were present in five patients only (0.5%). NMDAR antibodies of all Ig classes were equally prevalent in patients with and without psychosis. There were no significant differences in antibody prevalence in the different diagnostic categories, except for a higher odds ratio of being NMDAR antibody positive for patients without a specific psychiatric diagnosis. NMDAR IgG autoantibodies, which are known to be strongly associated with anti-NMDAR encephalitis, were rarely found. CASPR2 and GAD65 antibodies were more frequently encountered in the present study than previously reported. Further research on the clinical significance of anti-neuronal autoantibodies in patients with acute psychiatric symptoms is needed.

PREVALENCE OF ANTIBODY TO ALEUTIAN MINK DISEASE VIRUS IN EUROPEAN MINK (MUSTELA LUTREOLA) AND AMERICAN MINK (NEOVISON VISON) IN SPAIN.

The European mink (Mustela lutreola) has undergone a dramatic decline and is one of the most endangered mammals in the world. The invasive American mink (Neovison vison) is considered the main factor for this decline. However, the American mink's introduction and the subsequent ecological concurrence of the two species cannot solely explain the decline or disappearance of the European mink. Aleutian mink disease virus (AMDV) is the main health problem in fur farming worldwide, causing varied clinical syndromes that depend on the viral strain and host factors. Infection with AMDV has been speculated to contribute to the decline of the European mink, but a detailed study has not been performed. To assess the potential effects of AMDV infection on the conservation of the European mink, we surveyed AMDV antibody in samples from 492 native European mink and 1,735 feral American mink collected over 16 yr. The antibody prevalence in European mink was 32%. There were no statistically significant differences in antibody prevalence between sexes, among years, or among weight classes. For recaptured European mink, incidence of seroconversion (negative to positive) was 0.46 cases per animal-year at risk. For positive animals, the incidence of conversion from positive to negative was 0.18 cases per animal-year at risk. In 1,735 feral American minks, the overall prevalence was 32.4% and varied among the six wild populations studied. Infection with AMDV appears to be endemic, distributed across the entire ranges of both species, and no effects on the population dynamics of either species were observed.

Henipaviruses and Fruit Bats, Papua New Guinea

Henipaviruses and Fruit Bats, Papua New Guinea

Serosurvey for Antibody to Deerpox Virus in Five Cervid Species in Oregon, USA

Five cervid species in Oregon, USA were tested with a serum neutralization assay for antibody to deerpox virus (DPV). None of the 50 elk (Cervus elaphus ssp. roosevelti and nelsonii) had detectable antibody. Prevalence of antibody to DPV in the remaining species was: 52% (n=55) in black-tailed deer (Odocoileus hemionus columbianus), 32% (n= 59) in mule deer (O. hemionus hemionus), and 36% (n=50) in Columbian white-tailed deer (O. virginianus leucurus), with an overall antibody prevalence of 40.2% (n=164) for Odocoileus spp. Antibody-positive animals were identified throughout the state with no statistically significant differences among geographic regions. No statistically significant gender or age-related differences in antibody prevalence were demonstrated at either the genus or species level. This serosurvey indicates that exposure to DPV is common in Odocoileus populations in Oregon. Given the low rates of observed DPV-related disease, this high antibody prevalence suggests a pathogen of low virulence.

INBREEDING DEPRESSION INCREASES SUSCEPTIBILITY TO BOVINE TUBERCULOSIS IN LIONS: AN EXPERIMENTAL TEST USING AN INBRED–OUTBRED CONTRAST THROUGH TRANSLOCATION

Disease can dramatically influence the dynamics of endangered wildlife populations, especially when they are small and isolated, with increased risk of inbreeding. In Hluhluwe-iMfolozi Park (HiP), a small, enclosed reserve in South Africa, a large lion (Panthera leo) population arose from a small founder group in the 1960s and started showing conspicuous signs of inbreeding. To restore the health status of the HiP lion population, outbred lions were translocated into the existing population. In this study, we determined the susceptibility to bovine tuberculosis (bTB), and the prevalence of antibody to feline viruses of native lions, and compared the findings with those from translocated outbred lions and their offspring. Antibodies to feline herpesvirus, feline calicivirus, feline parvovirus, and feline coronavirus were present in the lion population, but there was no significant difference in antibody prevalence between native and translocated lions and their offspring, and these feline viruses did not appear to have an effect on the clinical health of HiP lions. However, feline immunodeficiency virus (FIV), which was previously absent from HiP, appears to have been introduced into the lion population through translocation. Within 7 yr, the prevalence of antibody to FIV increased up to 42%. Bovine tuberculosis posed a major threat to the inbred native lion population, but not to translocated lions and their offspring. More than 30% of the native lion population died from bTB or malnutrition compared with <2% of the translocated lions and their offspring. We have demonstrated that management of population genetics through supplementation can successfully combat a disease that threatens population persistence. However, great care must be taken not to introduce new diseases into populations through translocation.

EPIZOOTIOLOGY OF BRUCELLA INFECTION IN AUSTRALIAN FUR SEALS

Novel members of the bacterial genus Brucella have recently emerged as pathogens of various marine mammal species and as potential zoonotic agents. We investigated the epizootiology of Brucella infection in Australian fur seals (Arctocephalus pusillus doriferus) by establishing demographic and temporal variations in antibody prevalence, attempting isolation of the causative agent, and determining whether this potential pathogen is involved in frequent abortions observed in this pinniped species. Two competitive enzyme-linked immunosorbent assays (cELISAs), an indirect ELISA, and a fluorescence polarization assay (FPA) were used to test sera for Brucella antibodies. The FPA and cELISA proved suitable for use in this species. Significant differences in antibody prevalence were found between age classes of seals sampled between 2007 and 2009 at one colony. Pups sampled at this site (n=134) were negative for Brucella antibodies by all serologic tests but 17 of 45 (38%) of juveniles were antibody-positive. Antibody prevalence in adult females was significantly higher than in juveniles (P=0.044). Antibody prevalence for adult females between 2003 and 2009 varied significantly over time (P=0.011), and for individuals sampled between 2003 and 2005, the likelihood of pregnancy was greater in individuals positive for Brucella antibodies (P=0.034). Inflammatory lesions suggestive of infectious agents were found in 14 of 39 aborted Australian fur seal pups, but pathologic changes were not uniformly consistent for Brucella infection. Culture and PCR investigations on fetal tissues were negative for Brucella. Culture and PCR on selected fresh or frozen tissues from 36 juvenile and adult animals were also negative. We suspect that the prevalence of active infection with Brucella in Australian fur seals is low relative to antibody prevalence.

Differences in prevalence of antibodies to GAD and IA-2 and their titers at diagnosis in children with slowly and rapidly progressive forms of type 1 diabetes

We compared the frequencies of antibodies to GAD (GADA) and IA-2 (IA-2A) and their titers at diagnosis in 48 Japanese children with slowly progressive form of type 1 diabetes (SPT1D) and 70 children with rapidly progressive form of type 1 diabetes (RPT1D). High prevalences of both GADA and IA-2A were found at diagnosis in both the patients with SPT1D (70.8% and 75.0%), and those with RPT1D (71.4% and 71.9%). Most patients, regardless of the form of type 1 diabetes, were positive for both antibodies, though 6 of the 9 patients less than 5 years of age were negative for both antibodies. GADA titers below 50 U/ml were significantly more frequent in the patients with SPT1D (79.4% vs. 38.0%, p = 0.0002), and titers above 100 U/ml significantly more frequent in those with RPT1D (38.0% vs. 11.8%, p = 0.0081). No significant association was noted between the titers of IA-2A and the clinical form of type 1 diabetes. These results suggest that low GADA titers may reflect mild autoimmune destruction of beta-cells with slow disease progression. Titers of IA-2A do not appear to reflect the degree of autoimmune damage of the beta-cells.

Prevalence of antibodies against Toxoplasma gondii in roe deer from Spain

Roe deer ( Capreolus capreolus) is an important game animal in Spain. Sera from 278 roe deer from eight areas in mainland Spain were assayed for antibodies to Toxoplasma gondii by modified agglutination test (MAT). Titers of 1:25 or higher were found in 109 (39.2%) of 278 deer. No significant differences in antibody prevalence were found between sex or age categories. In contrast, significant differences in seroprevalence between locations were evident. Roe deer from the Northern coastal habitats (high humidity and roe deer density) had the highest prevalence, compared with low prevalence in Central Spain (arid areas and low roe deer density). There was a positive correlation between antibody prevalence and mean annual rainfall ( r s = 0.85, n = 8, P < 0.01). These findings have environmental and/or public health implications because venison can be an important meat source of T. gondii infections for humans and feral cats.

Factors associated with elevated serum concentrations of anti‐TPO antibodies in subjects with and without diffuse goitre. Results from the Ukrainian–American Cohort Study of Thyroid Cancer and Other Thyroid Diseases Following the Chornobyl Accident

To examine factors associated with the prevalence of elevated anti-thyroid peroxidase antibodies (ATPO) among iodine-deficient adolescents and young adults and test whether associations vary according to the presence of diffuse goitre. Subjects were members of the Ukrainian-American Cohort Study exposed to the Chornobyl accident whose (131)I thyroid dose estimates were below 0.2 Gy. The odds ratios (ORs) for ATPO above 60 U/ml were estimated using logistic regression models for a number of factors in the total population (N = 5133), and separately for thyroid disease-free subjects (N = 3875), those with diffuse goitre (N = 921), and diffuse goitre without autoimmune thyroiditis (AIT; N = 883). Elevated ATPO was found in 9.9% of the total population and ORs were significantly higher in females, older individuals, those examined in earlier calendar years, residents of Kyiv and Chernihiv oblasts, subjects with a family history of thyroid disease, higher thyroid ultrasound volume, suppressed or elevated TSH, blood collection in March to May, very low thyroglobulin (Tg), and shorter serum storage time. When thyroid disease-free subjects and those with diffuse goitre were compared, there were few differences in antibody prevalence, and after excluding individuals with AIT, the only difference was an increased prevalence of elevated ATPO at low urinary iodine in those with goitre alone. Although a number of factors are associated with the prevalence of elevated ATPO in our study group, with the exception of urinary iodine these factors are independent of goitre, and differences between thyroid disease-free subjects and those with diffuse goitre are largely due to AIT.

Prevalence of antibodies against canine distemper virus and canine parvovirus among foxes and wolves from Spain

Viral diseases can influence the population dynamics of wild carnivores and can have effects on carnivore conservation. Hence, a serologic survey was conducted in an opportunistic sample of 137 foxes ( Vulpes vulpes) and 37 wolves ( Canis lupus) in Spain for 1997–2007 to detect antibodies against canine distemper virus (CDV) and against canine parvovirus (CPV) by indirect ELISA. Antibodies against CDV were detected in 18.7% of the analyzed animals and antibodies against CPV in 17.2%. There was no difference in antibody prevalence to CDV between both species, even in the same region ( P > 0.05), but there was a significant difference in antibody prevalence to CPV between foxes (5.1%) and wolves (62.2%) ( P < 0.05). In fox populations there was a significant difference in antibody prevalence to CDV between geographic areas (Aragón 26.4%, La Mancha 7.8%, P < 0.05). In wolf populations there was significantly higher antibody prevalence against CPV ( P < 0.05) in Castilla y León (100%) than in the Cantabric region (53.3%). There was no significant sex or age-related difference in the antibody prevalence against CDV or CPV in foxes. These results indicate that contact with CDV is widespread among wild canid populations in Spain and that CPV is endemic in the Iberian wolf population. The implications of these results are briefly discussed.

Seroprevalence of Antibodies to Toxoplasma gondii in the Pennsylvania Bobcat (Lynx rufus rufus)

From 2000 to 2002 bobcat blood samples were collected, in association with the Pennsylvania Game Commission, during the recently reactivated bobcat hunting and trapping season. Sex, age, and county/township data were recorded for each animal. Blood was tested for antibodies to Toxoplasma gondii using the modified agglutination test. In the 2-yr study, 131 bobcat samples were collected in 14 Pennsylvania counties and 109 (83%) of these had antibodies to T. gondii (titer>or=25). A two-way Chi-Square test (95% confidence interval) yielded no significance differences in antibody prevalence between males (83%) and females (88%) or adults (83%) and juveniles (77%). All 14 counties had at least one bobcat with antibodies to T. gondii.

SEROLOGIC SURVEY FOR SELECTED DISEASE AGENTS IN WOLVES (CANIS LUPUS) FROM ALASKA AND THE YUKON TERRITORY, 1984–2000

Wolves (Canis lupus) were captured in several geographic areas of Alaska (USA) and the Yukon Territory (Canada) during 1984-2000. Blood was collected from 1,122 animals. Sera were tested for antibodies against infectious canine hepatitis virus (ICH), canine distemper virus (CDV), canine parvovirus (CPV), Francisella tularensis, and serovars of Leptospira interrogans. Antibody prevalence for ICH was >84% for all areas. Area-specific prevalences of antibodies ranged from 12% to 70% for CPV, from 0% to 41% for CDV, and from 4% to 21% for F. tularensis. There was no evidence of CDV exposure at the two southernmost locations in Alaska. Prevalence of antibodies for ICH increased slightly during the 16-yr course of the survey. There was essentially no evidence of exposure to L. interrogans. Prevalences of antibodies for both CPV and CDV were age-specific, with higher values in the adult cohort compared with the pup cohort. There were no sex-specific differences in prevalence of antibodies for any of the five disease agents.

Antibodies to canine distemper and phocine distemper viruses in polar bears from the Canadian arctic.

Serum samples collected from 200 polar bears (Ursus marititnus) from two populations in the Canadian arctic, the western Hudson Bay and Lancaster Sound populations, between 1989 and 1996, were tested for antibodies to canine distemper (CDV) and phocine distemper viruses (PDV) using virus neutralization. Antibodies to CDV and PDV were detected in 48 and six polar bears, respectively. All six bears that tested positive for PDV also tested positive for CDV; in only one case did the antibody titer for PDV exceed that of CDV. Differences in antibody prevalence to CDV were detected between populations and age classes but not sex or year of sampling.

Prevalence of hantavirus antibody in patients with chronic renal disease in Egypt

In Egypt, the etiology of chronic renal failure (CRF) is not well defined. A hospital-based case–control study was initiated in February 1998, to determine whether hantavirus infection is involved in chronic renal disease (CRD) in Egypt. The study enrolled 350 study patients with a history of CRF and 695 matched controls with CRD due to renal calculus or renal cancer, but with normal renal functions. Sera from cases and controls were tested for anti-hantavirus IgG using ELISA with a cell-lysate antigen from Hantaan virus prototype strain 76–118. A demographic questionnaire was completed for each study participant. Five of the 350 cases (1.4%), and seven of the 695 controls (1.0%) were antibody-positive to hantavirus, with a titer ≥1:400. The difference in antibody prevalence between the study cases and the control cases was not statistically significant ( P = 0.48). All antibody-positive study cases and controls had been exposed to rodents. Data indicated that in Egypt, hantavirus seroprevalence in CRD patients is low, and hantavirus infections do not appear to be a significant cause of CRF.

Serologic evidence of infection with granulocytic ehrlichiae in black bears in Pennsylvania.

Serum samples from 381 black bears (Ursus americanus) killed in Pennsylvania (USA) on 24 November 1997 were analyzed for antibodies reactive to the agent of human granulocytic ehrlichiosis (HGE; Ehrlichia sp.) by indirect immunofluorescence assay. Antibody reactivity to HGE antigen was detected in 21% (81/381) of the samples collected. Reactive samples were reported from 56% (14/25) of the counties where bear samples were collected. Endpoint antibody titer ranged from 1:8 to 1:16, 192, with a geometric mean titer of 1:582. There was no significant difference in antibody prevalence between male and female bears (P < 0.01). However, adult bears were significantly more likely to have reactive antibodies than juvenile bears (P < 0.01). Attempts to amplify and detect granulocytic ehrlichial DNA from corresponding bear blood clots (n = 181) through nested polymerase chain reaction assays were unsuccessful. Further studies are needed for identification of the pathogen-responsible for induction of HGE-reactive. This is the first description of antibodies reactive to the HGE agent in black bears and suggests these mammals are infected with the agent of HGE or an antigenically related ehrlichial species.

Viral diseases of northern ungulates

This paper describes viral diseases reported in northern ungulates and those that are a potential threat to these species. The following diseases are discussed: bovine viral diarrhoea/mucosal disease (BVD/MD), alphaherpesvirus infections, malignant catarrhal fever (MCF), poxvirus infections, parainfluenza type 3 virus infection, Alvsborg disease, foot-and-mouth disease, epizootic haemorrhage disease of deer and bluetongue disease, rabies, respiratory syncytial virus infection, adenovirus infection, hog-cholera, Aujeszky's disease and equine herpesvirus infections. There are no significant differences in antibody prevalence to BVDV among deer in habitats with high, intermediate and low density of cattle. In addition, sequence analysis from the BVDV isolated from roe deer (Capreolus capreolus) showed that this strain was unique within BVDV group I. Distinct BVDV strains might circulate in free-ranging roe deer populations in Germany and virus transmission may be independent of domestic livestock. Similar results have been obtained in a serological survey of alpha-herpesviruses in deer in Germany. Malignant catarrhal fever was studied in fallow deer (Cervus dama) in Germany: the seroprevalence and positive PCR results detected in sheep originating from the same area as the antibody-positive deer might indicate that sheep are the main reservoir animals. Contagious ecthyma (CE) is a common disease in domestic sheep and goats caused by the orf virus. CE has been diagnosed in Rocky Mountain bighorn sheep (Ovis canadensis), mountain goats (Oreamnos americanus), Dall sheep (Ovis dalli), chamois (Rupkapra rupi-capra), muskox {Ovibos moschatus) and reindeer (Rangifer tarandus). Most parainfluenza type 3 virus infections are mild or clinically undetectable. Serological surveys in wildlife have been successfully conducted in many species. In 1985, a new disease was identified in Swedish moose (Alces alces), designated as Alvsborg disease. This wasting syndrome probably has a multi-factorial etiology. Foot-and-mouth disease virus (FMDV) can infect deer and many other wild artiodactyls. Moose, roe deer and the saiga antelope (Saiga tatarica) are the main hosts of FMDV in the Russian Federation. In addition, serological evidence of a FMD infection without clinical disease was detected in red deer in France. Epizootic haemorrhage disease of deer (EHD) and bluetongue (BT) are acute non-contagious viral diseases of wild ruminants characterised by extensive haemorrhage. Culicoides insects are the main vectors. EHD and BT only play a minor role in Europe but both diseases are widespread in North America.

Cowdria ruminantium antibodies in acaricide-treated and untreated cattle exposed to Amblyomma variegatum ticks in The Gambia.

An indirect enzyme-linked immunosorbent assay (ELISA), based on the major antigenic protein I fragment B (MAPI-B) of Cowdria ruminantium, was used to assess seroprevalence in cattle in The Gambia. Two groups of 20 N'Dama and 20 Gobra zebu cattle were monitored for 12 months with flumethrin treatment and for another 10 months without acaricidal treatment. Two groups of 20 N'Dama and 20 Gobra cattle served as untreated controls. During the period of acaricidal treatment, the cumulative proportions of positive serum samples were 25.6 +/- 5.6% (+/- confidence interval) and 34.7 +/- 6.8% in treated N'Dama and Gobra cattle respectively; the proportion of positive sera in untreated cattle was 52.2 +/- 6.9% in N'Damas and 61.4 +/- 7.3% in Gobras. Within breed, difference in antibody prevalence between treated and untreated cattle was significant (P < 0.001) but between breed differences were not significant. In the 10 months following suspension of acaricide application, there was an increase of proportion of positive serum samples in previously treated N'Dama and Gobra cattle. In both previously treated and untreated animals the peak of positive seroreactions occurred during and subsequent to the period of activity of Amblyomma variegatum adults. Cumulative seroprevalences in previously treated N'Dama and Gobra cattle were 32.6 +/- 6.9% and 44.7 +/- 8.5%, respectively; in untreated animals seroprevalence was 38.6 +/- 7.2% in N'Dama and 65.3 +/- 8.4% in Gobra cattle. Throughout the study period, within the N'Dama breed, the seropositive rate in previously treated cattle did not differ from that in untreated animals. Conversely, within the Gobra breed, the number of positive seroreactions was higher (P < 0.002) in untreated animals than in previously treated cattle. These results provide a support for designing A. variegatum and heartwater control strategies, if necessary, in The Gambia in relation to cattle breeds.

Decay of passively acquired maternal antibodies against measles, mumps, and rubella viruses.

The decay of maternally derived antibodies to measles, mumps, and rubella viruses in Swiss infants was studied in order to determine the optimal time for vaccination. A total of 500 serum or plasma samples from infants up to 2 years of age were tested by enzyme-linked immunosorbent assay and fluorescent-antibody testing. The decline of antibody prevalence was slowest against the measles virus. By 9 to 12 months of age, only 5 of 58 (8.6%; 95% CI, 2.9 to 19.0) infants were antibody positive for the measles virus, and only 2 had levels above 200 mIU/ml. Mumps and rubella virus antibody seropositivity was lowest at 9 to 12 months of age with 3 of 58 (5. 2%; 95% CI, 1.1 to 14.4) infants and at 12 to 15 months with 1 of 48 (2.1%; 95% CI, 0.1 to 11.1) infants, respectively. Concentrations of passively acquired antibodies decreased rapidly within the first 6 months of life. We observed no significant differences in antibody prevalence or concentration according to gender in any age group. In conclusion, MMR vaccination at 12 instead of 15 months of age could reduce the pool of susceptible subjects in infancy and support the efforts to eliminate these infections, particularly in combination with a second vaccine dose before school entry.