ABSTRACT
Young children need increased access to dental prevention and care. Targeting high caries risk children first helps meet this need. The objective of this study was to develop a parent-completed, easy-to-score, short, accurate caries risk tool for screening in primary health care settings to identify children at increased risk for cavities. A longitudinal, prospective, multisite, cohort study enrolled (primarily through primary health care settings) and followed 985 (out of 1,326) 1-y-old children and their primary caregivers (PCGs) until age 4. The PCG completed a 52-item self-administered questionnaire, and children were examined using the International Caries Detection and Assessment Criteria (ICDAS) at 12 ± 3 mo (baseline), 30 ± 3 mo (80% retention), and 48 ± 3 mo of age (74% retention). Cavitated caries lesion (dmfs = decayed, missing, and filled surfaces; d = ICDAS ≥3) experience at 4 y of age was assessed and tested for associations with questionnaire items using generalized estimating equation models applied to logistic regression. Multivariable analysis used backward model selection, with a limit of 10 items. At age 4, 24% of children had cavitated-level caries experience; 49% were female; 14% were Hispanic, 41% were White, 33% were Black, 2% were other, and 10% were multiracial; 58% enrolled in Medicaid; and 95% lived in urban communities. The age 4 multivariable prediction model, using age 1 responses (area under the receiver operating characteristic curve = 0.73), included the following significant (P < 0.001) variables (odds ratios): child participating in public assistance programs such as Medicaid (1.74), being non-White (1.80-1.96), born premature (1.48), not born by caesarean section (1.28), snacking on sugary snacks (3 or more/d, 2.22; 1-2/d or weekly, 1.55), PCG cleaning the pacifier with juice/soda/honey or sweet drink (2.17), PCG daily sharing/tasting food with child using same spoon/fork/glass (1.32), PCG brushing their teeth less than daily (2.72), PCG's gums bleeding daily when brushing or PCG having no teeth (1.83-2.00), and PCG having cavities/fillings/extractions in past 2 y (1.55). A 10-item caries risk tool at age 1 shows good agreement with cavitated-level caries experience by age 4.
Subject(s)
Dental Caries , Pregnancy , Humans , Child , Female , Child, Preschool , Infant , Male , Dental Caries/diagnosis , Dental Caries/epidemiology , Dental Caries/prevention & control , Cohort Studies , Prospective Studies , Cesarean Section , Primary Health Care , DMF IndexABSTRACT
Equine influenza (EI) virus is one of the most economically important pathogens of respiratory diseases of horses worldwide. Despite availability of vaccines for control of EI, the highly contagious nature and variability properties of the virus mean global outbreaks occur. Thus, continuous surveillance programs, including seroprevalence studies of disease in different countries, may contribute to better control of the disease. In this study, the seroprevalence of equine influenza in 850 horses from Brazil was investigated. The serodiagnosis was based on the single radial hemolysis (SRH) assay using influenza A/equine/Richmond/1/2007 (H3N8) antigen. Antibodies against A/equine/Richmond/1/07 (H3N8) were detected in 44.7% (380/850, 95% CI: 41.4-48.1%) of horses. Seroprevalence was significantly lower (p = 0.001) in younger animals (< 5 years, 38.6%) than in "adult" animals (5-14 years, 52.1%). There was also a significant relationship between the year of sampling and seroprevalence (p < 0.0005). The mean SRH antibody value was 42.0 mm2 (range 4-238.9 mm2), with the majority of horses (95.3%) having an SRH value ≤ 150 mm2, which is considered an insufficient level for protection of equine hosts against influenza infections and potential virus shedding. These findings indicate the need to reinforce preventive/control measures against equine influenza in Brazil.
Subject(s)
Antibodies, Viral/blood , Disease Outbreaks/veterinary , Horse Diseases/epidemiology , Influenza A Virus, H3N8 Subtype/immunology , Orthomyxoviridae Infections/epidemiology , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/veterinary , Animals , Brazil , Female , Horse Diseases/virology , Horses/immunology , Horses/virology , Male , Orthomyxoviridae Infections/prevention & control , Retrospective Studies , Risk Factors , Seroepidemiologic Studies , Virus SheddingABSTRACT
BACKGROUND: Equine influenza virus is a highly contagious respiratory pathogen that causes pyrexia, anorexia, lethargy and coughing in immunologically naïve horses. Vaccines against equine influenza are available and vaccination is mandatory for horses that participate in affiliated competitions, but this group forms a small proportion of the total horse population. The aims of this study were to: i) identify the equine influenza vaccination rate as reported in 2016 by horse owners in the United Kingdom (UK); ii) examine the demographics of owners and horses which were associated with significantly lower influenza vaccination rates and iii) explore factors that influence horse owners' decisions around influenza vaccine uptake. RESULTS: Responses from 4837 UK horse owners who were responsible for 10,501 horses were analysed. An overall equine influenza vaccination rate of 80% (8385/10501) was reported. Several owner demographic characteristics were associated with significantly lower (p<0.05) reported equine influenza vaccination rates including: some geographical locations, increasing horse owner age, annual household income of less that £15,000 and owning more than one horse. Horse-related features which were associated with significantly lower reported equine influenza vaccination rates included age ranges of <4 years and > 20 years, use as a companion or breeding animal or leaving their home premises either never or at most once a year. The most common reasons cited for failing to vaccinate horses was no competition activity, lack of exposure to influenza and expense of vaccines. In contrast, the most common underlying reasons given by horse owners who vaccinated their horse were protection of the individual horse against disease, veterinary advice and to protect the national herd. Owners of vaccinated horses had less previous experience of an influenza outbreak or adverse reaction to vaccination compared with owners of unvaccinated horses. CONCLUSIONS: This study documented a high rate of equine influenza vaccination as reported by owners in a substantial number of horses in the UK, but this does not reflect the level of protection. Sub-populations of horses which were less likely to be vaccinated and the factors that influence each owner's decision around vaccination of their horses against equine influenza were identified, but may alter following the 2019 European influenza outbreak. This information may nevertheless help veterinary surgeons identify "at-risk" patients and communicate more personalised advice to their horse-owning clients. It may also influence educational campaigns about equine influenza directed to horse owners, which aim to improve uptake of vaccination against this pathogen.
Subject(s)
Health Knowledge, Attitudes, Practice , Horse Diseases/prevention & control , Influenza Vaccines/administration & dosage , Orthomyxoviridae Infections/veterinary , Vaccination/veterinary , Adult , Aged , Animals , Female , Horse Diseases/psychology , Horses , Humans , Male , Middle Aged , Orthomyxoviridae Infections/prevention & control , Orthomyxoviridae Infections/psychology , Vaccination/psychology , Young AdultABSTRACT
Expanded partnership with the medical community is a promising strategy for reducing disparities in dental caries among young children. However, no validated caries risk instrument exists for use in primary health care settings. To help resolve this gap, a 52-item caries risk questionnaire was developed and targeted to primary caregivers (PCGs) to test in a 3-y prospective study. To begin to understand the validity of the questionnaire items, the purpose of this study was to compare responses to the questionnaire based on key demographic characteristics known to be associated with disparities in caries experience (e.g., race/ethnicity and insurance status). A total of 1,323 one-year-old children were recruited primarily through 3 medical research networks. Baseline questionnaire responses were analyzed via logistic regression. The sample was 49% female. Its racial/ethnic makeup was as follows: 13% Hispanic, 37% White, 37% Black, and 13% other or multiracial. Sixty-one percent were enrolled in Medicaid, and 95% resided in urban communities. Mothers represented 94% of PCGs. There were significant differences ( P < 0.05) in baseline responses based on Medicaid status and race/ethnicity. As compared with those not enrolled in Medicaid, children in the Medicaid group were significantly more likely (after adjusting for race/ethnicity) to 1) go to sleep while nursing or drinking something other than water, 2) eat sugary snacks between meals, 3) consume sugary drinks between meals, 4) receive topical fluoride from a health professional, 5) visit the dentist, and 6) not have an employed adult in the household. PCGs of children enrolled in Medicaid were significantly more likely to be the mother, have bleeding gums, eat sugary snacks between meals, consume sugary drinks between meals, eat or drink something other than water before going to bed, and not get regular dental checkups. In conclusion, there are significant differences in caries risk questionnaire responses based on Medicaid status and race/ethnicity that provide construct and criterion validity to the developed caries risk tool (ClinicalTrials.gov NCT01707797).
Subject(s)
Dental Caries , Ethnicity , Health Status Disparities , Medicaid/statistics & numerical data , Adult , Asian People , Black People , Child , Child, Preschool , Female , Hispanic or Latino , Humans , Infant , Male , Native Hawaiian or Other Pacific Islander , Prospective Studies , Risk Factors , United States , White PeopleABSTRACT
Equine populations worldwide are at increasing risk of infection by viruses transmitted by biting arthropods, including mosquitoes, biting midges (Culicoides), sandflies and ticks. These include the flaviviruses (Japanese encephalitis, West Nile and Murray Valley encephalitis), alphaviruses (eastern, western and Venezuelan encephalitis) and the orbiviruses (African horse sickness and equine encephalosis). This review provides an overview of the challenges faced in the surveillance, prevention and control of the major equine arboviruses, particularly in the context of these viruses emerging in new regions of the world.
Subject(s)
Horse Diseases/virology , RNA Virus Infections/veterinary , RNA Viruses/classification , Animals , Global Health , Horses , RNA Virus Infections/prevention & control , RNA Virus Infections/virologyABSTRACT
Equine influenza is a highly contagious respiratory disease considered the most important respiratory disease in equids. Although influenza A virus (IAV) has caused outbreaks in equids worldwide, surveillance in these species in Spain has not been conducted. A cross-sectional study was carried out to determine the individual and herd prevalence of antibodies against H3N8 and H7N7 IAV in equids in Andalusia (southern Spain). Antibodies againsts IAV were measured by the single radial haemolysis assay. A spatial scan statistical analysis was carried out using a Bernoulli model. Risk factors associated with IAV infection were assessed by multivariate analysis. Antibodies to H3N8 IAV were detected in 241 out of 464 unvaccinated equids (51.9%; 95% CI: 47.4-56.5). Seropositivity against the H7N7 subtype IAV was not found in any of the analysed animals. Significantly higher seropositivity was found in geriatric (ORâ¯=â¯6.1, Pâ¯=â¯0.008, 95% CIâ¯=â¯1.6-23.1) and adult (ORâ¯=â¯4.8, Pâ¯<â¯0.001, 95% CIâ¯=â¯2.5-9.0) equids compared to young animals. Specific antibodies against A/equine/Shropshire/2010 (H3N8) or A/equine/Newmarket/5/2003 (H3N8) only were confirmed in 11 and 45 of the animals, respectively. The spatial analysis showed a statistically significant cluster centred in the west part of Andalusia. The results confirmed widespread H3N8 subtype IAV exposure in equine species in Andalusia. Conversely, the absence of seropositivity against H7N7 IAV obtained in the present study suggests that this subtype has not circulated in southern Spain in recent years. Because of the animal health and economic consequences of IAV in equids, further surveillance and molecular studies are required to monitor and characterize the most prevalent IAV circulating in these species in Spain.
Subject(s)
Horse Diseases/epidemiology , Orthomyxoviridae Infections/veterinary , Animals , Cross-Sectional Studies , Horse Diseases/virology , Horses , Influenza A Virus, H3N8 Subtype/physiology , Influenza A Virus, H7N7 Subtype/physiology , Orthomyxoviridae Infections/epidemiology , Orthomyxoviridae Infections/virology , Prevalence , Risk Factors , Seroepidemiologic Studies , Spain/epidemiologyABSTRACT
The Royal College of Veterinary Surgeons now lists 'How to evaluate evidence' as a day one competence for newly qualified vets. In this article, representatives from each of the veterinary schools in the UK discuss how the challenge of delivering and assessing the concepts of evidence-based veterinary medicine in a crowded undergraduate curriculum can be met.
Subject(s)
Education, Veterinary/organization & administration , Evidence-Based Medicine/education , Teaching/psychology , Curriculum , Humans , Schools, Veterinary , United KingdomABSTRACT
Canine parvovirus type 2 (CPV-2) is a highly contagious viral disease with three variants (CPV-2a, CPV-2b and CPV-2c) currently circulating in dogs worldwide. The main aim of this study was to determine the prevalent CPV-2 variant in faecal samples from 53 dogs presenting with acute gastroenteritis suspected to be and consistent with CPV-2 to Nigerian Veterinary Clinics in 2013-2014. Seventy-five per cent of these dogs tested positive for CPV-2 in a commercial antigen test and/or by PCR. Partial sequencing of the VP2 gene of six of these demonstrated them to be CPV-2a. Most of the dogs (60 per cent) were vaccinated, with 74 per cent of them puppies less than six months old.
ABSTRACT
Mathematical modelling of infectious disease is increasingly regarded as an important tool in the development of disease prevention and control measures. This article brings together key findings from various modelling studies conducted over the past 10 years that are of relevance to those on the front line of the battle against equine influenza.
Subject(s)
Horse Diseases/prevention & control , Models, Biological , Orthomyxoviridae Infections/veterinary , Animals , Horses , Influenza Vaccines/immunology , Orthomyxoviridae Infections/prevention & controlABSTRACT
Equine influenza virus is a major respiratory pathogen in horses, and outbreaks of disease often lead to substantial disruption to and economic losses for equestrian industries. The hemagglutinin (HA) protein is of key importance in the control of equine influenza because HA is the primary target of the protective immune response and the main component of currently licensed influenza vaccines. However, the influenza virus HA protein changes over time, a process called antigenic drift, and vaccine strains must be updated to remain effective. Antigenic drift is assessed primarily by the hemagglutination inhibition (HI) assay. We have generated HI assay data for equine influenza A (H3N8) viruses isolated between 1968 and 2007 and have used antigenic cartography to quantify antigenic differences among the isolates. The antigenic evolution of equine influenza viruses during this period was clustered: from 1968 to 1988, all isolates formed a single antigenic cluster, which then split into two cocirculating clusters in 1989, and then a third cocirculating cluster appeared in 2003. Viruses from all three clusters were isolated in 2007. In one of the three clusters, we show evidence of antigenic drift away from the vaccine strain over time. We determined that a single amino acid substitution was likely responsible for the antigenic differences among clusters.
Subject(s)
Evolution, Molecular , Hemagglutinin Glycoproteins, Influenza Virus/immunology , Influenza A Virus, H3N8 Subtype/genetics , Influenza A Virus, H3N8 Subtype/immunology , Orthomyxoviridae Infections/virology , Amino Acid Substitution , Animals , Antigens, Viral/classification , Antigens, Viral/immunology , Blotting, Western , Cells, Cultured , Dogs , Hemagglutination Inhibition Tests , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinins/immunology , Hemagglutinins/metabolism , Horses , Influenza A Virus, H3N8 Subtype/isolation & purification , Kidney/cytology , Kidney/metabolism , Kidney/virology , Orthomyxoviridae Infections/genetics , Orthomyxoviridae Infections/immunology , Phylogeny , RNA, Messenger/genetics , RNA, Viral/genetics , Reverse Transcriptase Polymerase Chain Reaction , Time FactorsABSTRACT
REASONS FOR PERFORMING STUDY: Surveillance of equine influenza viruses has suggested that strains included in currently licensed vaccines are a poor match for those predominantly circulating in the field. OBJECTIVE: To assess the ability of Duvaxyn IE-T Plus to provide cross protection against the newly evolved South Africa/4/03 (H3N8) strain of equine influenza virus. METHODS: The vaccine efficacy was evaluated by challenge infection with influenza strain A/eq/South Africa/4/03 (H3N8) 2 weeks after a primary course of 2 vaccinations with Duvaxyn IE-T Plus given at a 4-week interval. The outcome of challenge in vaccinated ponies was compared with that in unvaccinated animals. RESULTS: At the time of challenge, all vaccinated ponies had high levels of antibody to Newmarket/1/93, Newmarket/2/93 and South Africa/4/03 strains measured by single radial haemolysis. After challenge infection, there were statistically significantly decreased clinical scores and virus shedding was significantly lower in the vaccinated ponies compared to unvaccinated controls. CONCLUSION: Two doses of Duvaxyn IE-T Plus provides good clinical and virological protection against challenge with a variant virus 2 weeks after the 2 doses of vaccine. POTENTIAL RELEVANCE: When variant strains of equine influenza virus first emerge, booster immunisations with currently available vaccines may limit infection provided sufficiently high antibody levels are achieved, suggesting that vaccination in the face of an outbreak may be beneficial.
Subject(s)
Antibodies, Viral/blood , Horse Diseases/prevention & control , Influenza A Virus, H3N8 Subtype/immunology , Influenza Vaccines/immunology , Orthomyxoviridae Infections/veterinary , Animals , Disease Outbreaks/prevention & control , Disease Outbreaks/veterinary , Dose-Response Relationship, Immunologic , Horse Diseases/immunology , Horses , Immunization, Secondary/veterinary , Male , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/prevention & control , Time FactorsABSTRACT
Equine influenza virus (EIV) is a leading cause of respiratory disease in horses. Equine influenza infection induces a long-term immunity to re-infection. Recent strategies of vaccination aim to mimic this immunity by stimulating both antibody and cellular immune responses. Cell-mediated immunity (CMI) to influenza is well defined in man, but little has been done to characterise the responses in the horse. Additionally, the development of reliable assays for the measurement of equine CMI has lagged behind serological methods and vaccine development. In this study, two methods of measuring EIV-specific T lymphocyte responses have been developed. An EIV 'bulk' cytotoxic T lymphocytes (CTL) assay using equine dermal fibroblasts as target cells has been adapted from a method used in the 1980s. This method was also complemented with a new EIV-specific IFNgamma synthesis assay. When compared with the measurement of EIV-specific IFNgamma synthesis previously described, this method required the amplification of EIV-specific lymphocytes by culture and was sensitive enough to detect stimulation of EIV-specific T lymphocytes induced by experimental infection with EIV or vaccination with recombinant canarypox viruses coding for EIV-HA molecules. This study provides the tools to characterise the stimulation of CMI by the new generation of vaccines against equine influenza.
Subject(s)
Horses/immunology , Horses/virology , Influenza A Virus, H3N8 Subtype/immunology , Animals , Cells, Cultured , Horse Diseases/immunology , Horse Diseases/prevention & control , Horse Diseases/virology , Immunity, Cellular , Influenza A Virus, H3N8 Subtype/pathogenicity , Influenza Vaccines/immunology , Interferon-gamma/biosynthesis , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/prevention & control , Orthomyxoviridae Infections/veterinary , Orthomyxoviridae Infections/virology , Receptors, Virus/metabolism , T-Lymphocytes, Cytotoxic/immunology , T-Lymphocytes, Cytotoxic/virologyABSTRACT
In horses, equine influenza virus (EIV) is a leading cause of respiratory disease. Conventional inactivated vaccines induce a short-lived immune response. By comparison, natural infection confers a long-term immunity to re-infection. An aim of new equine influenza vaccines is to more closely mimic natural infection in order to achieve a better quality of immunity. A new live recombinant vaccine derived from the canarypox virus vector and expressing haemagglutinin genes of EIV (subtype H3N8) has been developed. Stimulation of the immune system was studied after immunisation with this canarypox-based vaccine and challenge infection by exposure to a nebulised aerosol of EIV. The humoral immune response was evaluated by measuring serum antibody levels using the single radial haemolysis (SRH) assay. The cellular immune response was assessed by the measurement of interferon gamma (IFN-gamma) synthesis in peripheral blood mononuclear cells (PBMC). Clinical signs of the disease (temperature, coughing, nasal discharge, dyspnoea, depression and anorexia) and virus excretion were monitored after challenge infection. Clinical signs and virus shedding were significantly reduced in vaccinates compared with unvaccinated controls. EIV-specific immunity was stimulated by vaccination with a recombinant vaccine as serological responses were detected after immunisation. This study also provided the first evidence for increased IFN-gamma protein synthesis in vaccinated ponies following challenge infection with EIV compared with control ponies.
Subject(s)
Canarypox virus/immunology , Horse Diseases/immunology , Horse Diseases/virology , Influenza A Virus, H3N8 Subtype/immunology , Orthomyxoviridae Infections/veterinary , Vaccination/veterinary , Viral Vaccines/immunology , Animals , Antibodies, Viral/biosynthesis , Antibodies, Viral/blood , Body Temperature/immunology , Canarypox virus/genetics , Horses , Interferon-gamma/biosynthesis , Interferon-gamma/blood , Interferon-gamma/immunology , Leukocytes, Mononuclear/immunology , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/prevention & control , Orthomyxoviridae Infections/virology , Vaccines, Synthetic/genetics , Vaccines, Synthetic/immunology , Vaccines, Synthetic/therapeutic use , Viral Vaccines/genetics , Viral Vaccines/therapeutic useABSTRACT
Equine influenza virus is a leading cause of respiratory disease in the horse. Equine influenza vaccines containing inactivated virus were first developed in the 1960s. Despite their intensive use, equine influenza outbreaks still continue to occur and therefore new strategies of vaccination are necessary to improve vaccine efficacy. Numerous methods of vaccination have been evaluated and commercialised in the horse, the most recent being the cold-adapted influenza virus and poxvirus-based vaccines. As a large animal model, the horse is also a useful species in which to evaluate the potential of new generations of influenza vaccine such as live-attenuated influenza virus engineered by reverse genetics. This report details the equine immune responses conferring protection against influenza. It then undertakes a selective review of different strategies of vaccination against equine influenza that have been developed over the last two decades and discusses factors that may influence the efficacy of vaccination. Finally it outlines progress in the development of a novel vaccination strategy against equine influenza using reverse genetics.
Subject(s)
Horse Diseases/prevention & control , Influenza A Virus, H3N8 Subtype/immunology , Influenza Vaccines/pharmacology , Orthomyxoviridae Infections/veterinary , Age Factors , Animals , Antibodies, Viral/biosynthesis , Female , Genetic Vectors , Horse Diseases/immunology , Horses , Immunity, Cellular , Immunity, Maternally-Acquired , Influenza A Virus, H3N8 Subtype/classification , Influenza A Virus, H3N8 Subtype/genetics , Influenza Vaccines/genetics , Models, Immunological , Molecular Epidemiology , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/prevention & control , Pregnancy , Vaccines, Attenuated/pharmacology , Vaccines, DNA/genetics , Vaccines, DNA/pharmacology , Vaccines, Inactivated/pharmacology , Vaccines, Subunit/genetics , Vaccines, Subunit/pharmacology , Vaccines, Synthetic/genetics , Vaccines, Synthetic/pharmacologyABSTRACT
Equine influenza is usually a transient and self-limiting disease. However, during an outbreak of equine influenza in the UK in 2003 there were reports of unusually severe clinical signs among unvaccinated animals. Two influenza-infected horses developed neurological signs, and one was subjected to euthanasia. Post-mortem examination of the brain revealed viral-type non-suppurative encephalitis, and influenza virus antigen was demonstrated by immunolabelling of sections of nasal mucosa. A syndrome known as influenza-associated encephalopathy has been described in man. Although not proved, the data suggest that similar disease mechanisms may operate in horses, and that equine influenza virus infection can result in encephalitis in the natural host, perhaps due to an aberrant host immune response.
Subject(s)
Disease Outbreaks/veterinary , Encephalitis/veterinary , Horse Diseases/virology , Influenza A virus/isolation & purification , Orthomyxoviridae Infections/veterinary , Amino Acid Sequence , Animals , Antigens, Viral/immunology , Brain/pathology , Brain/virology , Encephalitis/complications , Encephalitis/pathology , Female , Horse Diseases/pathology , Horses , Influenza A virus/genetics , Influenza A virus/immunology , Lectins/genetics , Male , Molecular Sequence Data , Orthomyxoviridae Infections/complications , Orthomyxoviridae Infections/pathology , Sequence AlignmentABSTRACT
Between March and May 2003, equine influenza virus infection was confirmed as the cause of clinical respiratory disease among both vaccinated and unvaccinated horses of different breeds and types in at least 12 locations in the UK. In the largest outbreak, 21 thoroughbred training yards in Newmarket, with more than 1300 racehorses, were affected, with the horses showing signs of coughing and nasal discharge during a period of nine weeks. Many of the infected horses had been vaccinated during the previous three months with a vaccine that contained representatives from both the European (A/eq/Newmarket/2/93) and American (A/eq/Newmarket/1/93) H3NN8 influenza virus lineages. Antigenic and genetic characterisation of the viruses from Newmarket and elsewhere indicated that they were all closely related to representatives of a sublineage of American viruses, for example, Kentucky/5/02, the first time that this sublineage had been isolated in the uk. In the recently vaccinated racehorses in Newmarket the single radial haemolysis antibody levels in acute sera appeared to be adequate, and there did not appear to be significant antigenic differences between the infecting virus and A/eq/Newmarket/1/93, the representative of the American lineage virus present in the most widely used vaccine, to explain the vaccine failure. However, there was evidence for significantly fewer infections among two-year-old horses than older animals, despite their having similar high levels of antibody, consistent with a qualitative rather than a quantitative difference in the immunity conveyed by the vaccination.