Equine piroplasmoses at the reintroduction site of the Przewalski's horse (Equus ferus przewalskii) in Mongolia

Piroplasmosis has been identified as a possible cause of mortality in reintroduced Przewalski's horses (Equus ferus przewalskii) in the Dsungarian Gobi (Mongolia). A cross-sectional and a longitudinal study were conducted in a representative sample (n = 141) of the resident domestic horse population and in 23 Przewalski's horses to assess the prevalence of Theileria equi and Babesia caballi. Piroplasms were detected in blood by light microscopy in 6.7% (95% confidence interval [CI]: 3.6-12.2%) of the domestic horse samples. Antibody prevalence was 88.6% (95% CI: 82.4-92.9%) for T. equi and 75.2% (95% CI: 67.4-81.6%) for B. caballi. Antibody prevalence did not change over time, but antibody prevalence for both piroplasms were significantly lower in animals less than 1 yr of age. For both piroplasms, the prevalence of presumably maternal antibodies (falling titers) in foals was 100%. Only one of 16 foals seroconverted against T. equi during the study period, despite that piroplasms were found in two other individuals. The incidence density (ID) of T. equi in foals was therefore 0.0012 seroconversions per horse day (95% CI: 0.00029-0.0057). In contrast, yearlings had an ID of 0.0080 (95% CI: 0.0049-0.010) for T. equi and 0.0064 (95% CI: 0.0036-0.0093) for B. caballi, and in seven individuals piroplasms were detected. The seroprevalence of both piroplasms rose from 20% in spring to 100% in autumn. Comparison of domestic and Przewalski's horses resulted in a standardized prevalence ratio (SPR) of 0.98 (95% CI: 0.80-1.24, not significant) for B. caballi; in contrast, the prevalence of T. equi in Przewalski's horses was significantly lower than expected (SPR = 0.51, 95% CI: 0.50-0.64).

Simulating the impact of four control strategies on the population dynamics of Neospora caninum infection in Swiss dairy cattle

A dynamic deterministic simulation model was developed to assess the impact of different putative control strategies on the seroprevalence of Neospora caninum in female Swiss dairy cattle. The model structure comprised compartments of "susceptible" and "infected" animals (SI-model) and the cattle population was divided into 12 age classes. A reference model (Model 1) was developed to simulate the current (status quo) situation (present seroprevalence in Switzerland 12%), taking into account available demographic and seroprevalence data of Switzerland. Model 1 was modified to represent four putative control strategies: testing and culling of seropositive animals (Model 2), discontinued breeding with offspring from seropositive cows (Model 3), chemotherapeutic treatment of calves from seropositive cows (Model 4), and vaccination of susceptible and infected animals (Model 5). Models 2-4 considered different sub-scenarios with regard to the frequency of diagnostic testing. Multivariable Monte Carlo sensitivity analysis was used to assess the impact of uncertainty in input parameters. A policy of annual testing and culling of all seropositive cattle in the population reduced the seroprevalence effectively and rapidly from 12% to <1% in the first year of simulation. The control strategies with discontinued breeding with offspring from all seropositive cows, chemotherapy of calves and vaccination of all cattle reduced the prevalence more slowly than culling but were still very effective (reduction of prevalence below 2% within 11, 23 and 3 years of simulation, respectively). However, sensitivity analyses revealed that the effectiveness of these strategies depended strongly on the quality of the input parameters used, such as the horizontal and vertical transmission factors, the sensitivity of the diagnostic test and the efficacy of medication and vaccination. Finally, all models confirmed that it was not possible to completely eradicate N. caninum as long as the horizontal transmission process was not interrupted.

Incidence of Neospora caninum and other intestinal protozoan parasites in populations of Swiss dogs

The protozoan parasite Neospora caninum is one of the most important abortifacient organisms in cattle worldwide. The dog is known to act as definitive host although its potential role as infection source for bovines still remains unelucidated. The aim of the present study was to compile initial epidemiological data on the prevalence and incidence of N. caninum in Swiss dogs acting as definitive hosts. Thus, 249 Swiss dogs were investigated coproscopically in monthly intervals over a period of 1 year. A total of 3289 fecal samples was tested by the flotation technique. Among these, 202 were shown to contain Sarcocystis sp. (6.1%), 149 Cystoisospora sp. (=Isospora sp.; 4.5%) and 25 Hammondia/Neospora-like oocysts (HNlO) (0.7%). All but one sample containing HNlO were from different dogs; one dog shed HNlO at two subsequent time points. Calculation of the yearly incidence for HNlO resulted in the surprisingly high value of 9.2%. Farm dogs exhibited a higher incidence for HNlO than urban family dogs. Thirteen out of the 25 HNlO-samples showed sporulation after 5 days incubation at room temperature. HNlO were further differentiated by species-specific PCR. However, all HNlO-samples were negative for N. caninum, Hammondia heydorni and Toxoplasma gondii. One reason may be the low oocyst density found in most fecal samples, which did not permit us to carry out PCR under optimal conditions. Three out of the 25 HNlO-cases contained enough oocysts to allow further enrichment and purification by the flotation technique. Subsequently, twenty to fifty sporulated HNlO-oocysts were orally administered to Meriones unguiculatus. All gerbils were seronegative for N. caninum at 5 weeks p.i. A N. caninum-seroprevalence of 7.8% was determined by ELISA upon 1132 serum samples collected from dogs randomly selected by veterinarians among their clinical patients.

Hepatitis A vaccines and the elderly

Hepatitis A virus (HAV) exposure in unprotected adults may cause severe and serious symptoms, with risk of both morbidity and mortality increasing with age. As seroprevalence of HAV is low in industrialised countries, and an increasing number of people, with an increasing median age, travel from areas of low HAV endemicity to high endemicity, pre-travel vaccination is warranted. Vaccination of the elderly against HAV, however, may be associated with reduced seroprotection, since the immune response decreases with age. Studies with monovalent hepatitis A vaccine or combined hepatitis A and B vaccine show good efficacy in adults in general. Few studies have assessed the immune response in older adults. The only prospective study with monovalent hepatitis A vaccine in the elderly showed a reduced seroprotection of approximately 65% after a single primary dose in subjects over the age of 50 years, while seroprotection was 98% in this age group after receiving a booster dose. The only prospective study with combined hepatitis A and B vaccine in younger subjects or older than 40 years showed similar seroprotection (99-100%) against HAV compared to a monovalent vaccine after receiving three doses. As data on seroprotection for HAV in the elderly are limited, further studies are needed to elucidate how optimal protection in the elderly can be achieved. In the mean time, based on the available data, the suggestion is made to screen elderly travellers to areas endemic for HAV for the presence of naturally acquired immunity, and, if found susceptible, be immunised well in advance of their trip, to allow time for post-vaccination antibody testing and/or administration of a second dose of the vaccine.

Serological survey of Toxoplasma gondii infection in free-ranging Eurasian lynx (Lynx lynx) from Sweden

To investigate the prevalence of Toxoplasma gondii infection in free-ranging Eurasian lynx (Lynx lynx) in Sweden, serosanguinous fluids and feces were collected from 207 carcasses of lynx killed or found dead from 1996 to 1998. Sera were tested for antibodies against T. gondii by the direct agglutination test, and 156 (75.4%) of the sera tested positive at antibody titers>or=40. Antibody prevalence was significantly lower in lynx originating from the northern parts of Sweden than in lynx from the more southern regions that are more densely populated by humans. Age-related differences also were found, with a significantly lower prevalence (55%) in juvenile (<1-yr-old) than in subadult and adult animals (82%). There was no significant difference in seroprevalence between males and females. Oocysts typical of T. gondii were not detected in any of the fecal samples.

[Heifer breeding farms as a source for spreading the BVD virus?]

It is well known that, in Switzerland, communal grazing of livestock on alpine pastures plays an important role in the spread of BVD virus. Analogously, we might expect that the communal raising on farms specialising in raising heifers of animals born on different farms would also favour the spread of BVDV. This study investigated whether a persistently infected (PI) breeding heifer kept on this type of farm over a period of 26 months would put the other animals at risk of being infected.The PI-animal was in contact with 75 heifers (here defined as contact animals) on this farm. Thirty-two of the contact animals that were probably pregnant (animals at risk of giving birth to a PI-calf) were moved to 8 different breeding farms (here defined as farms at risk). On these 8 farms, 246 calves were found to be at risk of being infected with BVDV. We examined 78 calves and investigated whether the move of the pregnant animals from their original farm had permitted the virus to spread to these 8 other farms.The contact animals had a seroprevalence of 92% and the animals at risk a seroprevalence of 100%. Only one PI-animal was found on the farms at risk.This BVD infection, however, occurred independently of the PI-breeding animal. Seropositive calves were found only on 2 farms. This study did not provide any proof for a spread of BVDV with the PI-breeding animal as a source; likewise, no persistent infection was proven to exist on the farms at risk. This result is likely to be representative for the endemic situation of BVD in Switzerland. Thus, PI-animals present on heifer raising farms infect calves well before servicing. Hence, no new PI-animals are generated, and the infection becomes self-limiting. When we reconstructed the animal movements between the farms and determined the animals to be examined with the aid of the Swiss national animal traffic database (TVD) we found the data of 37% of the heifers to be incomplete and failed to successfully establish the whereabouts of 3 animals.

Caprine Arthritis Encephalitis Complex

The caprine arthritis encephalitis virus (CAEV) is a lentivirus that persistently infects goats and sheep. The finding thatCAEV and Maedi-Visna viruses frequently cross the species barrier between goats and sheep, and vice versa, has changedour view of the epidemiology of these viruses that are now referred to assmall ruminant lentiviruses (SRLV).CAEV is transmitted from infected mothers to their offspring, mainly via ingestion of infected colostrum and milk. Thispermits the implementation of control measures based on the segregation ofnewborn kids immediately after birth thatsuccessfully cut the seroprevalence in infected flocks, eliminating CAEV induced clinical disease. CAEV induces overtpathology in about one third of the infected animals. The frequency of affected animals varies in different goat families,pointing to an important genetic component in this disease. The principal manifestations areencephalitis and interstitialpneumonia in young animals,whereas arthritis and mastitispredominate in adult goats. The immunopathologicalmechanisms leading to diseaseare to date unclear and involve the principal components ofthe immune system, i.e., theprofessional antigen presenting cells, which are the principal target of CAEV, and whose activity, e.g., cytokine production,is modulated by the infection, and the B- and T-cell immune responses that are alsomanipulated by the virus.In vivo,infected animals usually have low viral loads, indicating that virus replication istightly restricted by mechanisms thatremain unclear. Finally, the complex biology of SRLV makes them a great challenge for diagnostic laboratories.In this brief review, the literature pertinent toall these aspects is summarized and discussed.

Unsafe sex and increased incidence of hepatitis C virus infection among HIV-infected men who have sex with men: the Swiss HIV Cohort Study

BACKGROUND: Data on the incidence of hepatitis C virus (HCV) infection among human immunodeficiency virus (HIV)-infected persons are sparse. It is controversial whether and how frequently HCV is transmitted by unprotected sexual intercourse. METHODS: We assessed the HCV seroprevalence and incidence of HCV infection in the Swiss HIV Cohort Study between 1988 and 2004. We investigated the association of HCV seroconversion with mode of HIV acquisition, sex, injection drug use (IDU), and constancy of condom use. Data on condom use or unsafe sexual behavior were prospectively collected between 2000 and 2004. RESULTS: The overall seroprevalence of HCV infection was 33% among a total of 7899 eligible participants and 90% among persons reporting IDU. We observed 104 HCV seroconversions among 3327 participants during a total follow-up time of 16,305 person-years, corresponding to an incidence of 0.64 cases per 100 person-years. The incidence among participants with a history of IDU was 7.4 cases per 100 person-years, compared with 0.23 cases per 100 person-years in patients without such a history (P<.001). In men who had sex with men (MSM) without a history of IDU who reported unsafe sex, the incidence was 0.7 cases per 100 person-years, compared with 0.2 cases per 100 person-years in those not reporting unsafe sex (P=.02), corresponding to an incidence rate ratio of 3.5 (95% confidence interval, 1.2-10.0). The hazard of acquiring HCV infection was elevated among younger participants who were MSM. CONCLUSIONS: HCV infection incidence in the Swiss HIV Cohort Study was mainly associated with IDU. In HIV-infected MSM, HCV infection was associated with unsafe sex.

Longterm survey (7 years) in a population at risk for Lyme borreliosis: what happens to the seropositive individuals?

In 1986, a 26% seroprevalence of IgG- anti-Borrelia burgdorferi antibodies was observed among 950 orienteers and the incidence of new clinical infections was 0.8%. In 1993, a total of 305 seropositive orienteers were reexamined. During that time, 15 cases (4.9%) of definite/probable Lyme disease occurred in this seropositive group (12 skin manifestations and 3 monoarticular joint manifestations). Among the 12 definite cases, 9 showed new clinical infections (7 EM, 1 acrodermatitis chronica atrophicans, 1 arthritis), and 3 were recurrent (2 EM, 1 arthritis). The annual incidence (0.8%) in this seropositive group was identical to the incidence observed among the whole population in 1986. The individual antibody titer decreased slightly but the seroreversion rate was low (7%). Serology was not very helpful in identifying clinical cases and evolutions, and it can be stated, that a positive serology is much more frequent in this risk group than clinical disease.

Autoantibodies directed against bactericidal/permeability-increasing protein in patients with cystic fibrosis: association with microbial respiratory tract colonization

BACKGROUND: Cystic fibrosis (CF) is associated with the appearance of serum autoantibodies directed against bactericidal/permeability-increasing protein (BPI). OBJECTIVES: To determine the age-specific seroprevalence rates of anti-BPI-IgG and IgA in a population of patients with CF and to correlate anti-BPI antibody concentrations with microbial respiratory tract colonization and pulmonary function variables at the time of serum sampling and 6 years thereafter. METHODS: Determination of BPI antibodies of the IgG and IgA isotypes using a commercial enzyme-linked immunosorbent assay in sera of a CF serum bank of 1992; correlation of anti-BPI antibody concentrations with age, clinical score, pulmonary function variables in 1992 and 1998, total serum immunoglobulin isotype concentrations and respiratory tract colonization with Pseudomonas aeruginosa and Aspergillus spp. RESULTS: Seventy-one patients (age in 1992, 14.1 +/- 7.5 years) were studied. Reactivities for anti-BPI-IgG and IgA were found in 28 (39%) and 26 (37%) patients, respectively. The seroprevalence of anti-BPI-IgA, but not IgG, increased significantly with age. P. aeruginosa colonization was associated with elevated concentrations of anti-BPI-IgG (P = 0.003) and IgA (P = 0.037). There were significant negative correlations between pulmonary function variables (vital capacity, forced expiratory volume in 1 s) in 1992 and 1998, respectively, and concentrations of anti-BPI-IgG or IgA in a multiple regression analysis. Anti-BPI-IgG, but not IgA, remained significantly associated with P. aeruginosa colonization (P = 0.006) and with reduced vital capacity (P = 0.01) in 1998 after correction for total serum isotype concentration. CONCLUSIONS: Anti-BPI-IgG are strongly associated with concurrent P. aeruginosa colonization and with long term restrictive pulmonary function abnormalities.

[Occurrence of Trichinella spp. in wild boar in Switzerland]

Trichinellosis is a worldwide occurring zoonosis caused by the intracellular nematode Trichinella spp. One of the main infection sources in Europe is raw or undercooked meat from wild boar. Trichinella britovi is prevalent in wild carnivores in Switzerland, thus a possible inclusion of wild boar in this wildlife cycle cannot be excluded. In order to assess the prevalence of Trichinella infection in wild boar, we tested 1,458 animals with both parasitological and serological methods. In none of the animals Trichinella-larvae could be recovered by the artificial digestion method (prevalence of larvae: 0 %; 95 % CI 0.0 - 0.3). Antibodies in meat juice were detected in 57 animals using a standardized E/S-Ag-ELISA. However, in the confirmatory westernblot, only 3 animals remained seropositive (seroprevalence: 0.2 %; 95 % CI 0.07 %-0.60 %). The occurrence of wild boar positive for anti-Trichinella-antibodies indicates that meat inspection for Trichinella-larvae in this species is important to prevent human infections.

Bovine viral diarrhea virus in free-ranging wild ruminants in Switzerland: low prevalence of infection despite regular interactions with domestic livestock

ABSTRACT: BACKGROUND: In the frame of an eradication program for bovine viral diarrhea (BVD) in Swiss livestock, the question was raised whether free-ranging wildlife could threaten the success of this sanitary measure. Therefore, we conducted serological and virological investigations on BVD virus (BVDV) infections in the four indigenous wild ruminant species (roe deer, red deer, Alpine chamois and Alpine ibex) from 2009 to 2011, and gathered information on interactions between wild and domestic ruminants in an alpine environment by questionnaire survey. RESULTS: Thirty-two sera out of 1'877 (1.7%, 95% confidence interval [CI] 1.2-2.4) were seropositive for BVDV, and a BVDV1 sub genotype h virus was found in a seropositive chamois (0.05%, 95% CI 0.001-0.3). The seropositive animals originated from sub-alpine or alpine regions and significantly more seropositive red deer, chamois and ibex than roe deer were found. There were no statistically significant differences between sampling units, age classes, genders, and sampling years. The obtained prevalences were significantly lower than those documented in livestock, and most positive wild ruminants were found in proximity of domestic outbreaks. Additionally, BVDV seroprevalence in ibex was significantly lower than previously reported from Switzerland. The survey on interspecific interactions revealed that interactions expected to allow BVDV transmission, from physical contacts to non-simultaneous use of the same areas, regularly occur on pastures among all investigated ruminant species. Interactions involving cervids were more often observed with cattle than with small ruminants, chamois were observed with all three domestic species, and ibex interacted mostly with small ruminants. Interactions related to the use of anthropogenic food sources were frequently observed, especially between red deer and cattle in wintertime. CONCLUSIONS: To our knowledge, this is the first report of BVDV RNA isolated from an Alpine chamois. Nevertheless, our results suggest that BVDV infections are only sporadic in Swiss wild ruminants, despite regular occurrence of interactions with potentially infected livestock. Overall, serological, virological and ethological data indicate that wildlife is currently an incidental spill-over host and not a reservoir for BVDV in Switzerland.

Kinetics of maternally acquired anti-hepatitis A antibodies: prediction of waning based on maternal or cord blood antibody levels

BACKGROUND Timing is critical for efficient hepatitis A vaccination in high endemic areas as high levels of maternal IgG antibodies against the hepatitis A virus (HAV) present in the first year of life may impede the vaccine response. OBJECTIVES To describe the kinetics of the decline of anti-HAV maternal antibodies, and to estimate the time of complete loss of maternal antibodies in infants in León, Nicaragua, a region in which almost all mothers are anti-HAV seropositive. METHODS We collected cord blood samples from 99 healthy newborns together with 49 corresponding maternal blood samples, as well as further blood samples at 2 and 7 months of age. Anti-HAV IgG antibody levels were measured by enzyme immunoassay (EIA). We predicted the time when antibodies would fall below 10 mIU/ml, the presumed lowest level of seroprotection. RESULTS Seroprevalence was 100% at birth (GMC 8392 mIU/ml); maternal and cord blood antibody concentrations were similar. The maternal antibody levels of the infants decreased exponentially with age and the half-life of the maternal antibody was estimated to be 40 days. The relationship between the antibody concentration at birth and time until full waning was described as: critical age (months)=3.355+1.969 × log(10)(Ab-level at birth). The survival model estimated that loss of passive immunity will have occurred in 95% of infants by the age of 13.2 months. CONCLUSIONS Complete waning of maternal anti-HAV antibodies may take until early in the second year of life. The here-derived formula relating maternal or cord blood antibody concentrations to the age at which passive immunity is lost may be used to determine the optimal age of childhood HAV vaccination.

Epidemiology of Brucellosis and Q Fever in Linked Human and Animal Populations in Northern Togo

BACKGROUND: Although brucellosis (Brucella spp.) and Q Fever (Coxiella burnetii) are zoonoses of global importance, very little high quality data are available from West Africa. METHODS/PRINCIPAL FINDINGS: A serosurvey was conducted in Togo's main livestock-raising zone in 2011 in 25 randomly selected villages, including 683 people, 596 cattle, 465 sheep and 221 goats. Additionally, 464 transhumant cattle from Burkina Faso were sampled in 2012. The serological analyses performed were the Rose Bengal Test and ELISA for brucellosis and ELISA and the immunofluorescence assay (IFA) for Q Fever Brucellosis did not appear to pose a major human health problem in the study zone, with only 7 seropositive participants. B. abortus was isolated from 3 bovine hygroma samples, and is likely to be the predominant circulating strain. This may explain the observed seropositivity amongst village cattle (9.2%, 95%CI:4.3-18.6%) and transhumant cattle (7.3%, 95%CI:3.5-14.7%), with an absence of seropositive small ruminants. Exposure of livestock and people to C. burnetii was common, potentially influenced by cultural factors. People of Fulani ethnicity had greater livestock contact and a significantly higher seroprevalence than other ethnic groups (Fulani: 45.5%, 95%CI:37.7-53.6%; non-Fulani: 27.1%, 95%CI:20.6-34.7%). Appropriate diagnostic test cut-off values in endemic settings requires further investigation. Both brucellosis and Q Fever appeared to impact on livestock production. Seropositive cows were more likely to have aborted a foetus during the previous year than seronegative cows, when adjusted for age. This odds was 3.8 times higher (95%CI: 1.2-12.1) for brucellosis and 6.7 times higher (95%CI: 1.3-34.8) for Q Fever. CONCLUSIONS: This is the first epidemiological study of zoonoses in Togo in linked human and animal populations, providing much needed data for West Africa. Exposure to Brucella and C. burnetii is common but further research is needed into the clinical and economic impact.

Survey of bluetongue virus infection in free-ranging wild ruminants in Switzerland.

BACKGROUND In 2006, bluetongue virus serotype 8 (BTV-8) was detected for the first time in central Europe. Measures to control the infection in livestock were implemented in Switzerland but the question was raised whether free-ranging wildlife could be a maintenance host for BTV-8. Furthermore Toggenburg orbivirus (TOV), considered as a potential 25th BTV serotype, was detected in 2007 in domestic goats in Switzerland and wild ruminants were considered a potential source of infection. To assess prevalences of BTV-8 and TOV infections in wildlife, we conducted a serological and virological survey in red deer, roe deer, Alpine chamois and Alpine ibex between 2009 and 2011. Because samples originating from wildlife carcasses are often of poor quality, we also documented the influence of hemolysis on test results, and evaluated the usefulness of confirmatory tests. RESULTS Ten out of 1,898 animals (0.5%, 95% confidence interval 0.3-1.0%) had detectable antibodies against BTV-8 and BTV-8 RNA was found in two chamois and one roe deer (0.3%, 0.1-0.8%). Seroprevalence was highest among red deer, and the majority of positive wild animals were sampled close to areas where outbreaks had been reported in livestock. Most samples were hemolytic and the range of the optical density percentage values obtained in the screening test increased with increasing hemolysis. Confirmatory tests significantly increased specificity of the testing procedure and proved to be applicable even on poor quality samples. Nearly all samples confirmed as positive had an optical density percentage value greater than 50% in the ELISA screening. CONCLUSIONS Prevalence of BTV-8 infection was low, and none of the tested animals were positive for TOV. Currently, wild ruminants are apparently not a reservoir for these viruses in Switzerland. However, we report for the first time BTV-8 RNA in Alpine chamois. This animal was found at high altitude and far from a domestic outbreak, which suggests that the virus could spread into/through the Alps. Regarding testing procedures, hemolysis did not significantly affect test results but confirmatory tests proved to be necessary to obtain reliable prevalence estimates. The cut-off value recommended by the manufacturer for the screening test was applicable for wildlife samples.