High Seroprevalence Rates Research Articles

Toxoplasmosis in camelids: the last 20 years

Toxoplasmosis is a universal zoonosis caused by an obligate intracellular parasite, Toxoplasma gondii. One of its main manifestations is abortion in humans and animals. The present review aims to clarify the situation of the disease in camelids in different countries across the four continents of the world (Africa, Asia, America and Europe) over the past twenty years. The research strategy involved collecting all published data during this period, focusing on the prevalence of Toxoplasma gondii infection and genotyping in different camelid species, as well as analyzing the various identified risk factors. This review provides a comprehensive epidemiological analysis of Toxoplasma gondii infection worldwide, making it a valuable resource for researchers. In total, 81 studies published between 2004 and 2024 involving 22040 camelids from 23 countries were included for the final analyses (Seropositivity studies covered 21844 camelids, while genotyping studies were performed on 585 camelids). The overall global seroprevalence of Toxoplasma gondii infection in the Camelidae family was 28.76% with 6284 positive cases. The highest seroprevalence rate was in Europe (73.01%), followed by Africa (39.26%), Asia (22.16%) and finally America (22.05%). The current article highlighted a high seroprevalence of Toxoplasma gondii infection in camelids worldwide, thus emphasizing the significant role these animals can play in the transmission cycle of this zoonotic disease. Therefore, it is essential to implement prevention and control measures as well as to raise public awareness to mitigate the public health impact of the disease.

Immunologic assessment of the impact of SARS-CoV-2 vaccine booster doses on humoral immunity: a cross-sectional study in morocco

To assess the impact of the SARS-CoV-2 booster dose on the immune response against COVID-19, we conducted a cross-sectional study in the Casablanca-Settat region of Morocco. The study included 2,802 participants from 16 provinces, all of whom had received three doses of a SARS-CoV-2 vaccine. IgG antibodies targeting the S1 RBD subunit of the SARS-CoV-2 spike protein were quantified using the SARS-CoV-2 IgG II Quant assay and measured on the Abbott Architect i2000SR instrument. Adjusted seroprevalence of anti-RBD antibodies showed that participants who received two doses of ChAdOx1-S followed by a BBIBP-CorV booster had a seroprevalence rate of 99.68% (95% CI: 99.39–99.83%), while those who received a BNT162b2 booster had a rate of 99.67% (95% CI: 99.38–99.82%). Both rates were higher than those observed with other vaccination regimens. The evaluation of booster dose effects revealed significant differences in anti-RBD antibody levels across various vaccination regimens: two doses of BBIBP-CorV compared to three doses of BBIBP-CorV (P < 0.0001), two doses of BNT162b2 versus three doses of BNT162b2 (P = 0.023), two doses of ChAdOx1-S versus two doses of ChAdOx1-S with a BNT162b2 booster (P = 0.023), and two doses of BBIBP-CorV versus two doses of BBIBP-CorV with a BNT162b2 booster (P < 0.0001). However, no significant difference was found between two doses of ChAdOx1-S and three doses of ChAdOx1-S (P = 0.23). Participants with prior SARS-CoV-2 exposure who received two doses of ChAdOx1-S followed by either a BBIBP-CorV or BNT162b2 booster showed higher levels of anti-RBD IgG antibodies (P = 0.042 and P = 0.001, respectively). Interestingly, individuals with comorbidities who received the BNT162b2 booster dose exhibited a significantly stronger humoral response (P < 0.05). In conclusion, our findings highlight the effectiveness of the BNT162b2 booster dose in eliciting a strong immune response. The high seroprevalence rates achieved with both BNT162b2 and BBIBP-CorV boosters reflect the country’s robust vaccination strategy.

Seroprevalence of canine distemper virus antibodies in free-roaming dogs in Cambodia.

Canine distemper virus (CDV) can infect a wide range of mammalian carnivores and can cause severe illness and death. Domestic dogs may be an important source of this virus for endangered wild carnivores. The objective of this study was to establish the presence of CDV in rural areas of Cambodia bordering three established protected habitats, and to determine the seroprevalence of CDV in free-roaming dogs inhabiting these areas. These protected areas are home to endangered carnivores, such as Dhole (Cuon alpinus), and virus transmission from free-ranging dogs may pose a risk to endangered species. Blood samples collected from dogs were tested for CDV IgG antibodies using the Anigen rapid CDV commercial test kit (Bionote). We report the seroprevalence of CDV as 40% of sampled free-ranging dogs. This is the first documentation of CDV in the buffer zone of important protected areas in Cambodia. The high seroprevalence rate suggests a substantial risk of disease transmission to wildlife, highlighting the need for targeted interventions. We recommend further investigation into the role of dogs in the epidemiology of CDV in Cambodian wildlife and the consideration of vaccination programs for domestic dogs in these regions.

Seroprevalence of brucellosis in cows and buffaloes

Brucellosis poses a significant zoonotic risk to humans and animals, and is caused by the Gram-negative bacteria of the Brucella species. In cows and buffaloes, infection is typically attributed to Brucella abortus, often resulting in abortion during late pregnancy and posing a subsequent risk of sterility in females. The current study aimed to assess the seroprevalence of brucellosis in cows and buffaloes in district Kasur, Pakistan. A total of 400 blood samples were randomly collected from cows and buffaloes in the district. The Rose Bengal Plate Test (RBPT) was initially employed for screening the blood serum samples of each animal, with Indirect ELISA serving as a confirmatory test. Higher seroprevalence rates were observed in females compared to those in males in both tests. Sex-wise, higher incidence of brucellosis in cows was observed, with a prevalence of (7%)/(5%) in females compared to that (2%)/(1%) in males, as detected by the RBPT and iELISA tests, respectively. Similarly, buffaloes exhibited a higher prevalence of brucellosis in females, with rates (10%)/ (8%) compared to (3%)/(1%) in males, via RBPT and iELISA, respectively. A total of 200 cow and 200 buffalo samples were analyzed, that revealed a seroprevalence of (4.5%)/(3%) in cows and (6.5%)/(4.5%) in buffaloes, respectively, using RBPT and iELISA. Overall, out of a total of 400 serum samples, 22 from cows and buffaloes were tested positive through RBPT, while 15 samples from both species were seropositive via iELISA. The overall seroprevalence of brucellosis in the district was found to be 5.5%/3.75% through RBPT and iELISA, respectively. This study highlights a significant challenge for the livestock being rared in district Kasur.

Seroprevalence of Arboviruses in a Malaria Hyperendemic Area in Southern Mali.

Diagnostics for febrile illnesses other than malaria are not readily available in rural sub-Saharan Africa. This study assessed exposure to three mosquito-borne arboviruses-dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV)-in southern Mali. Seroprevalence for DENV, CHIKV, and ZIKV was analyzed by detection of IgG antibodies and determined to be 77.2%, 31.2%, and 25.8%, respectively. Among study participants, 11.3% were IgG-positive for all three arboviruses. DENV had the highest seroprevalence rate at all sites; the highest seroprevalence of CHIKV and ZIKV was observed in Bamba. The seroprevalence for all three arboviruses increased with age, and the highest seroprevalence was observed among adults older than 50 years. The prevalence of Plasmodium spp. in the cohort was analyzed by microscopy and determined to be 44.5% (N = 600) with Plasmodium falciparum representing 95.1% of all infections. This study demonstrates the co-circulation of arboviruses in a region hyperendemic for malaria and highlights the needs for arbovirus diagnostics in rural sub-Saharan Africa.

Antibody Seroprevalence to Spotted Fever Group Rickettsiae in Miraflores, Colombia: A Cross-Sectional Study in Humans and Dogs.

Tick-borne disease burdens are increasing globally, impacting mostly rural and vulnerable communities. Among the most important emerging tick-borne pathogens are the Rickettsia species within the spotted fever group (SFGR) because of their genetic diversity and high lethality rate. Colombia is highly affected by SFGR despite not being reportable diseases; thus, research and clinical management are neglected. Although some departments have demonstrated high seroprevalence rates, in others, such as Boyacá Department, seroprevalence is unknown. Rickettsioses have not been described in Boyacá since 1943, and conversations with local physicians raised suspicions of recent undiagnosed disease compatible with rickettsiosis in some rural areas of the department, warranting epidemiological investigation. Using biobanked human and canine samples from a previous 2021 vector-borne disease study in Miraflores municipality, Boyacá, we had an opportunity to unearth SFGR's exposure in the region. Samples were evaluated using IgG indirect fluorescent assays against SFGR and complemented by survey questionnaires evaluating associated factors. Findings yielded first-time SFGR serological evidence in Boyacá with a 26.5% seroprevalence among dogs and a 20.4% among humans. Human and dog seroprevalences were positively associated, suggesting the presence of domestic transmission. Owning a greater number of domestic animals (prevalence ratio adjusted for all measured factors [aPR], 1.52) and living near crop fields (aPR, 7.77) were associated with an increased likelihood of household seropositivity. Our findings are consistent with the literature in Colombia, uncovering a suspected region where the disease is endemic. Future studies are warranted to continue defining high-risk areas to determine public health intervention plans.

Study of the circulation and properties of the West Nile virus in Russia in 2022

Introduction. The relevance of the study is due to the need to assess the real expansion of West Nile fever (WNF) in Russia, analyze the manifestations of epizootic and epidemic processes and study the population structure of West Nile virus (WNV).&#x0D; Aim. To obtain objective data on the intensity of WNV circulation in certain territories of Russia and study the properties of the isolated strains of the pathogen.&#x0D; Materials and methods. 4564 samples of field material from 23 subjects of the Russian Federation and 1547 samples of clinical material from 12 subjects of the Russian Federation were examined. A set of laboratory diagnostic methods was used: ELISA, RT-PCR, virological, sequencing.&#x0D; Results. In 20 out of 1331 (1.5%) examined febrile patients, IgM antibodies to WNV were detected, including positive cases identified for the first time in the Karachay-Cherkess Republic, Tver and Vladimir regions. The presence of immunity to WNV was found on average in 8.6% of 11 federal subjects' population with high seroprevalence rates in Zaporozhye (24,5%), Tula (15,4%) and Kursk (11,1%) regions. Low-avidity IgG antibodies were detected in 44 (33,1%) samples from a population of 9 federal subjects. Intensive circulation of WNV lineage 2 in the epizootic cycle in the southern part of European Russia was confirmed. 12 WNV isolates were obtained, including those isolated for the first time in the Republic of Crimea, the Karachay-Cherkess Republic and the Stavropol Territory. The heterogeneity of circulating WNF causative agent's strains related to the two clades of the WNV lineage 2 formed in 2021 and 2022 was established.&#x0D; Conclusion. In the course of comprehensive monitoring studies, a new northern border of the WNF range was established, which as of 2022 passes through the territory of the Tver region. Data from seroepidemiological studies, including the detection of low-avidity IgG antibodies, confirm fairly intense, but undiagnosed contact of the population of the European part of Russia with the WNF pathogen. In the southern region of the European part of Russia, WNV genotype 2 predominantly circulates, belonging to at least two clades formed in 2021 and 2022.

Seroprevalence, Blood Chemistry, and Patterns of Canine Parvovirus, Distemper Virus, Plague, and Tularemia in Free-Ranging Coyotes (Canis latrans) in Northern New Mexico, USA.

Wildlife diseases have implications for ecology, conservation, human health, and health of domestic animals. They may impact wildlife health and population dynamics. Exposure rates of coyotes (Canis latrans) to pathogens such as Yersinia pestis, the cause of plague, may reflect prevalence rates in both rodent prey and human populations. We captured coyotes in north-central New Mexico during 2005-2008 and collected blood samples for serologic surveys. We tested for antibodies against canine distemper virus (CDV, Canine morbillivirus), canine parvovirus (CPV, Carnivore protoparvovirus), plague, tularemia (Francisella tularensis), and for canine heartworm (Dirofilaria immitis) antigen. Serum biochemistry variables that fell outside reference ranges were probably related to capture stress. We detected antibodies to parvovirus in 32/32 samples (100%), and to Y. pestis in 26/31 (84%). More than half 19/32 (59%) had antibodies against CDV, and 5/31 (39%) had antibodies against F. tularensis. We did not detect any heartworm antigens (n = 9). Pathogen prevalence was similar between sexes and among the three coyote packs in the study area. Parvovirus exposure appeared to happen early in life, and prevalence of antibodies against CDV increased with increasing age class. Exposure to Y. pestis and F. tularensis occurred across all age classes. The high coyote seroprevalence rates observed for CPV, Y. pestis, and CDV may indicate high prevalence in sympatric vertebrate populations, with implications for regional wildlife conservation as well as risk to humans via zoonotic transmission.

The evolution and interpretation of seroprevalence of SARS-CoV-2 antibodies among South African blood donors from the Beta to Omicron variant-driven waves.

Confirmed COVID-19 diagnoses underestimate the total number of infections. Blood donors can provide representative seroprevalence estimates, which can be leveraged into reasonable estimates of total infection counts and infection fatality rate (IFR). Blood donors who donated after each of three epidemic waves (Beta, Delta and first Omicron waves) were tested for anti-SARS-CoV-2 nucleocapsid antibodies using the Roche Elecsys anti-SARS-CoV-2 total immunoglobulin assay. Roche Elecsys anti-spike antibody testing was done for the post-Omicron sampling. Prevalence of antibodies was estimated by age, sex, race and province and compared to official case reporting. Province and age group-specific IFRs were estimated using external excess mortality estimates. The nationally weighted anti-nucleocapsid seroprevalence estimates after the Beta, Delta and Omicron waves were 47% (46.2%-48.6%), 71% (68.8%-73.5%) and 87% (85.5%-88.4%), respectively. There was no variation by age and sex, but there were statistically and epidemiologically significant differences by province (except at the latest time point) and race. There was a 13-fold higher seroprevalence than confirmed case counts at the first time point. Age-dependent IFR roughly doubled for every 10 years of age increase over 6 decades from 0.014% in children to 6.793% in octogenarians. Discrepancies were found between seroprevalence and confirmed case counts. High seroprevalence rates found among Black African donors can be ascribed to historical inequities. Our IFR estimates were useful in refining previous large disagreements about the severity of the epidemic in South Africa. Blood donor-based serosurveys provided a valuable and efficient way to provide near real-time monitoring of the ongoing SARS-CoV-2 outbreak.

Seroprevalence of human adenovirus type 5 neutralizing antibodies in the Philippines.

Human adenovirus (HAdV), particularly the HAdV type 5 (HAdV-5), has been extensively utilized in the development of vector vaccines due to its high immunogenicity, good safety profile, and ease of propagation. However, one of the main challenges in its use is the presence of pre-existing immunity among vaccine recipients. Pre-existing neutralizing antibodies (NAbs) can prevent the uptake of HAdV-5 vectors and reduce vaccine efficacy. Hence, this study investigated the seroprevalence of NAbs against HAdV-5 in urban and rural regions of the Philippines. Luciferase-based neutralization assay was performed on 391 plasma/serum samples. Out of these samples, 346 or 88.5% were positive for HAdV-5 NAbs, and the majority of them (56.8%) had high titers against the virus. Among the regions included in this study, Bicol (Region V) had the highest seroprevalence rate (94.1%). Our findings show that a significant number of adults in the Philippines have pre-existing immunity against HAdV-5. This supports the recommendation that vaccination programs in the country should consider implementing vaccination techniques, such as a prime-boost regimen or addition of booster doses, to address the potential negative effects of pre-existing HAdV-5 immunity in the efficacy of adenoviral vector-based vaccines.

Latent Toxoplasmosis among Breast Cancer Patients in Jahrom, South of Iran.

Reactivation of latent toxoplasmosis is the main cause of severe infection among immunocompromised patients, including patients with cancer. Hence, this study is aimed at screening the status of Toxoplasma gondii infection among breast cancer patients by serological and molecular methods and determining their associated risk factors in Jahrom County, Fars Province, south of Iran. One hundred and seven women with breast cancer (aged 34 to 80 years) were screened for anti-T. gondii antibodies (IgG and IgM) during 2019-2020. A questionnaire regarding demographic factors was filled out by participants. Molecular detection was performed by polymerase chain reaction (PCR) using the primer pair targeting the repetitive element (RE) gene of T. gondii. The risk factors and demographic data were analyzed by SPSS software (ver. 20, Chicago, IL, USA) using the Chi-squared test. Anti-T. gondii IgG was detected in 45.8% (49/107) of the patients, which indicates latent infection, but anti-T. gondii IgM and PCR were negative in all samples. Demographic factors revealed a statistically significant increased T. gondii seropositivity among nonmenopause cancer patients (P < 0.0005), patients without previous breast cancer (P = 0.0001), and human epidermal growth factor receptor 2- (HER2-) negative patients (P = 0.00002). As such, patients with a history of previous abortions and who were at stages II, III, and IIII of cancer had higher seropositivity rates than patients without a history of previous abortions or who were at stage I cancer, but the statistical analysis was not significant. We did not find a statistically significant association between T. gondii seropositivity and other risk factors of toxoplasmosis (e.g., education level, type of water source, washing raw fruits and vegetables, consumption of raw or undercooked meat, and contact with soil, cats, and domestic animal). A high seroprevalence rate of latent T. gondii infection was detected among patients with breast cancer; hence, these patients may be at high risk for reactivation of latent infection. Screening of T. gondii infection is recommended to detect active infection among patients with malignancies.

Seroprevalence of Toscana and sandfly fever Sicilian viruses in humans and livestock animals from western Saudi Arabia

High seroprevalence rates of several phleboviruses have been reported in domestic animals and humans in sandfly-infested regions. Sandfly Fever Sicilian virus (SFSV) and Toscana virus (TOSV) are two of these viruses commonly transmitted by Phlebotomus sandflies. While SFSV can cause rapidly resolving mild febrile illness, TOSV could involve the central nervous system (CNS), causing diseases ranging from aseptic meningitis to meningoencephalitis. Sandfly-associated phleboviruses have not been investigated before in Saudi Arabia and are potential causes of infection given the prevalence of sandflies in the country. Here, we investigated the seroprevalence of SFSV and TOSV in the western region of Saudi Arabia in samples collected from blood donors, livestock animals, and animal handlers. An overall seroprevalence of 9.4% and 0.8% was found in humans for SFSV and TOSV, respectively. Seropositivity was significantly higher in non-Saudis compared to Saudis and increased significantly with age especially for SFSV. The highest seropositivity rate was among samples collected from animal handlers. Specifically, in blood donors, 6.4% and 0.7% tested positive for SFSV and TOSV nAbs, respectively. Animal handlers showed higher seroprevalence rates of 16% and 1% for anti-SFSV and anti-TOSV nAbs, respectively, suggesting that contact with livestock animals could be a risk factor. Indeed, sera from livestock animals showed seropositivity of 53.3% and 4.4% in cows, 27.5% and 7.8% in sheep, 2.2% and 0.0% in goats, and 10.0% and 2.3% in camels for SFSV and TOSV, respectively. Together, these results suggest that both SFSV and TOSV are circulating in the western region of Saudi Arabia in humans and livestock animals, albeit at different rates, and that age and contact with livestock animals could represent risk factors for infection with these viruses.

Patterns in the development of collective immunity to SARS-CoV-2 during the COVID-19 pandemic

The ongoing coronavirus disease (COVID-19) pandemic over the past three years has caused close attention to the problem of herd immunity, which is understood as: "resistance to the spread of a contagious disease within a population or herd". Collective immunity is formed both as a result of infection (natural spread of the pathogen in a population of susceptible individuals) and as a result of the use of specific vaccines. During the COVID-19 pandemic, both mechanisms for the formation of collective immunity were realized. In the first wave, there was a natural formation of collective immunity to the virus following recoveries from COVID-19 caused by pandemic spread of SARS-CoV-2. Starting from December 2020, the widespread use of specific vaccines against SARS-CoV-2 began in the USA, Great Britain, China, Russia, and a number of other countries. This launched the process of post-vaccination collective immunity formation; its features have depended on the vaccine types implemented. Currently, in those countries where vaccination and revaccination of recovered patients is widely carried out, immunity is "hybrid" in nature. Several commonalities should be noted in the pandemic experience: a somewhat regular, periodic (wavelike) nature of the COVID-19 epidemic process; changes in pathogen genetics in variants in all countries; and expansive mass vaccination programs in many populations. From these, we can draw some conclusions about the general trend for all countries in the formation of collective immunity during the pandemic: At the beginning of the pandemic in 2020, overall population seroprevalence did not exceed 20%. Other findings were: the highest seroprevalence rates were noted in the children's age group; pronounced regional differences were revealed; and the highest indicators were noted among medical workers. Collective immunity developed as a result of infection or illness, and in the majority of seropositive volunteers, it was represented by antibodies to both antigens. At the height of the pandemic in the summer of 2021, population seroprevalence reached 50%. This was due to both a significant number of convalescents and the start of mass vaccination campaigns. In all countries, specific differences in seroprevalence (by age, region, profession) leveled out, leading to more uniformity. During this period, the formation of "hybrid" immunity is clearly prominent, and the proportion of individuals with antibodies to RBD alone increased (due to vaccination with vector vaccines). Later, mass vaccination, as well as involvement of most of the population in the epidemic process due to the emergence of the highly contagious Omicron strain, raised the level of collective immunity to 80-90%. This led to a sharp decrease in COVID-19 incidence in the second half of 2022 in all countries participating in the study. In the later stages of the pandemic (2022-2023), almost 90% of seropositive volunteers had hybrid immunity, reflected as antibodies to both antigens (Nc, RBD).

Engineering Adenoviral Vectors with Improved GBM Selectivity.

Glioblastoma (GBM) is the most common and aggressive adult brain cancer with an average survival rate of around 15 months in patients receiving standard treatment. Oncolytic adenovirus expressing therapeutic transgenes represent a promising alternative treatment for GBM. Of the many human adenoviral serotypes described to date, adenovirus 5 (HAdV-C5) has been the most utilised clinically and experimentally. However, the use of Ad5 as an anti-cancer agent may be hampered by naturally high seroprevalence rates to HAdV-C5 coupled with the infection of healthy cells via native receptors. To explore whether alternative natural adenoviral tropisms are better suited to GBM therapeutics, we pseudotyped an HAdV-C5-based platform using the fibre knob protein from alternative serotypes. We demonstrate that the adenoviral entry receptor coxsackie, adenovirus receptor (CAR) and CD46 are highly expressed by both GBM and healthy brain tissue, whereas Desmoglein 2 (DSG2) is expressed at a low level in GBM. We demonstrate that adenoviral pseudotypes, engaging CAR, CD46 and DSG2, effectively transduce GBM cells. However, the presence of these receptors on non-transformed cells presents the possibility of off-target effects and therapeutic transgene expression in healthy cells. To enhance the specificity of transgene expression to GBM, we assessed the potential for tumour-specific promoters hTERT and survivin to drive reporter gene expression selectively in GBM cell lines. We demonstrate tight GBM-specific transgene expression using these constructs, indicating that the combination of pseudotyping and tumour-specific promoter approaches may enable the development of efficacious therapies better suited to GBM.

Population-based sero-epidemiological investigation of SARS-CoV-2 infection in Somalia

ObjectivesTo explore the burden of coronavirus disease 2019 (COVID-19) in Somalia by measuring the seroprevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the general population. MethodsWe recruited a convenience sample of 2751 participants from among individuals attending outpatient and inpatient departments of public health facilities, or their accompanying family members. Participants were interviewed to collect sociodemographic data and provided a blood sample. We calculated seropositivity rates overall and by sex, age group, state, residence, education and marital status. We used logistic regression analysis – odds ratios and 95% confidence intervals (CI) – to investigate sociodemographic correlates of seropositivity. ResultsThe overall seropositivity rate was 56.4% (95% CI 54.5–58.3%), while 8.8% of participants reported being previously diagnosed with COVID-19 by July 2021. In the regression analysis, after controlling for covariates, urban residence was significantly asscoiated with seropositivity: OR = 1.74 (95% CI: 1.19–2.55). ConclusionsOur results show a high seroprevalence rate of SARS-CoV-2 in the Somali population (56.4%), and indicate that many infections have not been captured by the country’s surveillance system resulting in considerable under-reporting.

The seroprevalence of African horse sickness virus, and risk factors to exposure, in domestic dogs in Tshwane, South Africa.

Dogs are the only non-equid species to develop the fatal form of African horse sickness (AHS). Research conducted in 2013 questioned the long-held belief that naturally occurring cases of AHS in dogs were contracted exclusively through the ingestion of contaminated horse meat. Culicoides midges, the vector of AHS virus (AHSV) for horses, have an aversion to dog blood meals and dogs were believed to be dead-end or incidental hosts. More recently, dog mortalities have occurred in the absence of horse meat consumption and vector transmission has been suspected. The current study is a retrospective serological survey of AHSV exposure in dogs from an endemic area. Dog sera collected from dogs (n=366) living in the city of Tshwane, Gauteng Province, South Africa, were randomly selected from a biobank at a veterinary teaching hospital, corresponding to the years 2014-2019. The study used a laboratory in-house indirect recombinant VP7 antigen-based enzyme-linked immunosorbent assay (iELISA) with a test cut-off calculated from AHSV exposure-free dog sera (n=32). Study AHSV seroprevalence was 6 % (22/366) with an estimated true prevalence of 4.1 % (95 % confidence interval (CI) =1.3-8.1 %). Incidence was estimated for dogs with multiple serological results with seroconversion occurring at a rate of 2.3 seroconversions per 10 dog years at risk (95 % CI = 0.6-6.2). A subsection of the study sera was tested with AHSV viral neutralisation test (VN) (n=42) for serotype determination. Antibodies to AHSV serotype 6 were most prevalent (90 %) in VN seropositive dogs (n=20) with most dogs seemingly subclinically infected (>95 %). Seroprevalence descriptively varied by year and identified risk factors were annual rainfall >754mm (odds ratio (OR) =5.76; 95 % CI =2.22 - 14.95; p<0.001), medium human population densities, 783-1663 people/km2 (OR = 7.14; 95 % CI = 1.39 - 36.73; p=0.019) and 1664-2029 people/km2 (OR = 6.74; 95 % CI = 1.40 - 32.56; p=0.018), and the month of March (OR = 5.12; 95 % CI = 1.41 - 18.61; p=0.013). All identified risk factors were consistent with midge-borne transmission to dogs. The relatively high seroprevalence and seroconversion rates suggest frequent exposure of dogs to AHSV and indicates the need to investigate the role dogs might play in the overall epidemiology and transmission of AHSV.

Molecular and serological evidence of Crimean-Congo hemorrhagic fever orthonairovirus prevalence in livestock and ticks in Cameroon.

Despite a high fatality rate in humans, little is known about the occurrence of Crimean-Congo hemorrhagic fever virus (CCHFV) in Cameroon. Hence, this pioneer study was started with the aim of determining the prevalence of CCHFV in domestic ruminants and its potential vector ticks in Cameroon. A cross-sectional study was carried out in two livestock markets of Yaoundé to collect blood and ticks from cattle, sheep, and goats. CCHFV-specific antibodies were detected in the plasma using a commercial ELISA assay and confirmed using a modified seroneutralization test. Ticks were screened for the presence of orthonairoviruses by amplification of a fragment of the L segment using RT-PCR. Phylogeny was used to infer the genetic evolution of the virus. Overall, 756 plasma samples were collected from 441 cattle, 168 goats, and 147 sheep. The seroprevalence of CCHFV was 61.77% for all animals, with the highest rate found in cattle (433/441, 98.18%) followed by sheep (23/147, 15.65%), and goats (11/168, 6.55%), (p-value < 0.0001). The highest seroprevalence rate was found in cattle from the Far North region (100%). Overall, 1500 ticks of the Rhipicephalus (773/1500, 51.53%), Amblyomma (341/1500, 22.73%), and Hyalomma (386/1500, 25.73%) genera were screened. CCHFV was identified in one Hyalomma truncatum pool collected from cattle. Phylogenetic analysis of the L segment classified this CCHFV strain within the African genotype III. These seroprevalence results call for additional epidemiological studies on CCHFV, especially among at-risk human and animal populations in high-risk areas of the country.

Seroprevalence and Risk Factors for Bovine Coronavirus Infection among Dairy Cattle and Water Buffalo in Campania Region, Southern Italy

Cattle and water buffalo are the main livestock species that are raised in the Campania region, southern Italy, and they contribute significantly to the regional rural economy. Currently there are limited data on the prevalence of relevant impact infections, such as bovine coronavirus (BCov), an RNA virus that causes acute enteric and respiratory disease. Although these diseases are described primarily in cattle, there have been reports of spillovers to other ruminants, including water buffalo. Here, we determined the seroprevalence of BCoV in cattle and water buffalo in the Campania region of southern Italy. An overall seroprevalence of 30.8% was determined after testing 720 sampled animals with a commercial enzyme-linked immunosorbent assay. A risk factor analysis revealed that the seropositivity rates in cattle (49.2%) were higher than in water buffalo (5.3%). In addition, higher seroprevalence rates were observed in older and purchased animals. In cattle, housing type and location were not associated with higher seroprevalence. The presence of BCoV antibodies in water buffalo was associated with the practice of co-inhabiting with cattle, demonstrating that this practice is incorrect and promotes the transmission of pathogens between different species. Our study found a considerable seroprevalence, which is consistent with previous research from other countries. Our results provide information on the widespread distribution of this pathogen as well as the risk factors that are involved in its transmission. This information could be useful in the control and surveillance of this infection.

SARS-CoV-2 seroprevalence among children in Latvia: A cross-sectional study.

Coronavirus disease 2019 (COVID-19) is a major global health concern. In contrast to adults, the course of the disease has been observed to be mild or even asymptomatic in children. It is therefore both clinically and epidemiologically important to measure the seroprevalence in children and adolescents to discern the overall morbidity of the disease and to compare these findings with similar data collected globally. We conducted a cross-sectional study between March and July of 2022 at the Children Clinical University Hospital in Riga, Latvia, to evaluate the seroprevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Participants aged 0 to 18 years were enrolled during hospitalization for reasons other than COVID-19. The levels of SARS-CoV-2 spike protein and nucleocapsid antibodies were measured in blood samples. The possibility of transplacental antibody transport was evaluated by directly interviewing the mothers of participants aged 18 months and younger. Various demographic and epidemiological risk factors and their association with seroprevalence were analyzed. Positive SARS-CoV-2 nucleocapsid antibodies were designated the main criterion for seropositivity. Of 200 enrolled children, 173 were found to be seropositive, resulting in an overall seroprevalence of 86.5%. The highest seroprevalence was detected in children and adolescents aged 12 to 18 years. With the progression of the COVID-19 pandemic, the seroprevalence in children has increased significantly. We found that almost 1-third of seropositive children in our study population were unaware of being previously infected with SARS-CoV-2 due to an asymptomatic course of the disease. Our study findings pertaining to high seropositivity among children and adolescents might be beneficial for public authorities to adapt epidemiological strategies and prevention measures. The high seroprevalence rate reported here and in many other populations around the world suggests that COVID-19 will likely become one of the many seasonal viral infections.

A seroepidemiological survey of adenovirus type 7 circulation among healthy adults in China and in Sierra Leone, West Africa.

Adenovirus type 7 (HAdV7) is one of the most pathogenic human adenoviruses (HAdVs) and can cause severe illness and even death, particularly in people with weakened immune systems. Many countries worldwide have experienced epidemics of this highly contagious pathogen, including China and Sierra Leone; however, studies describing the seroprevalence of anti-HAdV7 neutralizing antibodies (nAbs) are still lacking. Herein, we established an efficient neutralization assay based on a recombinant luciferase-expressing HAdV7 virus (HAd7-Luc) to monitor historical HAdV7 infections and predict outbreak distributions. Among the 2,350 serum samples collected from eight sites in China and Sierra Leone in this cross-sectional serological survey, the overall proportion of anti-HAdV7-seropositive individuals was nearly 60%, with higher seroprevalence rates in Sierra Leone than in China. Regionally, HAdV7 nAb titers were higher in China than in Sierra Leone and showed a geographic variation across different regions. Regardless of the location, the seropositive rate of HAdV7 nAb was lower than that of HAdV5 nAb, as was the nAb titer. The prevalence rates of antibodies against HAdV7 and HAdV5 were both related to age but not to sex. In addition, serologic cross-reactions were rarely observed among people infected with HAdV7 and HAdV5. These results indicate a humoral immune response acquired through endemic HAdV7 infection and enrich the understanding of not only the epidemiological prevention and control of HAdV7 but also the clinical application of HAdV7-based vaccines or gene therapy tools.