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Topic:Disease Transmission
Disease transmission in horses refers to the spread of infectious agents such as bacteria, viruses, fungi, and parasites among equine populations. These pathogens can be transmitted through various routes, including direct contact, vector-borne transmission, or environmental exposure. Factors influencing disease transmission include horse density, management practices, and biosecurity measures. Understanding the mechanisms and conditions that facilitate the spread of diseases is essential for developing effective prevention and control strategies. This page compiles peer-reviewed research studies and scholarly articles that investigate the modes of transmission, risk factors, and management practices related to infectious diseases in horses.
West Nile virus infection of horses. West Nile virus (WNV) is a flavivirus closely related to Japanese encephalitis and St. Louis encephalitis viruses that is primarily maintained in nature by transmission cycles between mosquitoes and birds. Occasionally, WNV infects and causes disease in other vertebrates, including humans and horses. West Nile virus has re-emerged as an important pathogen as several recent outbreaks of encephalomyelitis have been reported from different parts of Europe in addition to the large epidemic that has swept across North America. This review summarises the main features of WNV infection in the horse, ...
Haemolysins of Salmonella, their role in pathogenesis and subtyping of Salmonella serovars. Haemolysin patterns of 175 strains of different Salmonella enterica subspecies enterica serovars isolated from different animal sources and places were determined using 11 different blood agar media made with either non-washed horse/sheep erythrocytes or with washed erythrocytes of cattle, sheep, horse, goat, rabbit, guinea pig, and human A, O and B blood groups. Study on 47 strains belonging to 10 serovars of Salmonella from buffalo meat (buffen), 42 strains of 11 serovars from goat meat (chevon): 16 strains of Salmonella enterica serovar Paratyphi B and 25 of S. enterica serovar Paratyphi B ...
Assessment of electrical charge on airborne microorganisms by a new bioaerosol sampling method. Bioaerosol sampling is necessary to monitor and control human exposure to harmful airborne microorganisms. An important parameter affecting the collection of airborne microorganisms is the electrical charge on the microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on airborne microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and po...
Use of a real-time polymerase chain reaction-based fluorogenic 5′ nuclease assay to evaluate insect vectors of Corynebacterium pseudotuberculosis infections in horses. To develop and use a sensitive molecular assay for detecting the phospholipase D (PLD) exotoxin gene of Corynebacterium pseudotuberculosis in an attempt to identify insect vectors that may be important in transmission of clinical disease in horses. Methods: 2,621 flies of various species. Methods: A real-time polymerase chain reaction (PCR)-based fluorogenic 5' nuclease (TaqMan) system (ie, TaqMan PCR assay) was developed for the detection of the PLD gene in insects. Flies were collected monthly (May to November 2002) from 5 farms in northern California where C. pseudotuberculosis infection in...
Seasonal development of Cyathostominae larvae on pasture in a northern temperate region of the United Kingdom. A study following the development of Cyathostominae from egg to the infective larval third stage was conducted from April to December 2001 in west central Scotland. Duplicate samples (1 kg) of naturally infected faeces were placed on a 78 cm2 plot each week on a cyathostomin-free pasture. Subsamples of the grass surrounding the faecal plot were collected weekly on four occasions and the number of larvae obtained determined. Few larvae were recovered in the first week of development of individual plots, followed by a rise in the numbers of larvae in second, third and fourth weeks of development...
Alternate circulation of recent equine-2 influenza viruses (H3N8) from two distinct lineages in the United States. Phylogenetic and antigenic analyses indicate that recent circulating equine-2 influenza viruses in the United States have been alternating between two genetic and antigenic distinct lineages since 1996. The evolution rates for these two lineages, the Kentucky and the Florida lineage, are very similar. For the earlier isolates in the Kentucky lineage, there are multiple and sequential nonsynonymous substitutions at antigenic sites B and D. However, there are no changes at any of these antigenic sites for KY98 and OK00. In the Florida lineage, except for NY99 with one amino acid substitution at ...
Eastern tent caterpillars (Malacosoma americanum) cause mare reproductive loss syndrome. A new equine abortigenic disease, mare reproductive loss syndrome (MRLS), was recognized and significantly impacted the Ohio Valley in the springs of 2001 and 2002. MRLS caused approximately 330 million US dollars in losses in 2001. An epidemiological investigation of MRLS associated occurrence of the disease with exposure to eastern tent caterpillars (M. americanum). This work investigates the epidemiological association between M. americanum and MRLS to determine if this association was correlative or causative. A pilot study and simulated exposure to M. americanum and their excreta on pastu...
Association between cribbing and entrapment of the small intestine in the epiploic foramen in horses: 68 cases (1991-2002). To determine whether there was an association between a history of cribbing and epiploic foramen entrapment (EFE) of the small intestine in horses. Methods: Retrospective study. Methods: 68 horses examined at the University of Illinois or the University of Liverpool veterinary teaching hospitals. Methods: For horses examined at the University of Illinois that underwent surgery because of strangulating small intestine lesions, information about cribbing was obtained through telephone calls with owners. For horses examined at the University of Liverpool that underwent surgery for colic for any r...
West Nile virus: an overview of its spread in Europe and the Mediterranean basin in contrast to its spread in the Americas. West Nile (WN) virus is a mosquito-transmitted flavivirus. It is widely distributed in Africa, the Middle East, Asia, and southern Europe and was recently introduced to North America. Birds are involved in the cycle of transmission as amplifying hosts. Humans and horses are considered accidental dead-end hosts. WN fever was initially considered a minor arbovirosis, usually inducing a nonsymptomatic or a mild flu-like illness in humans, but some cases of encephalitis associated with fatalities were reported in Israel in the 1950s. After two silent decades, several human and equine outbreaks of ...
Avian host preference by vectors of eastern equine encephalomyelitis virus. An important variable in the amplification and escape from the enzootic cycle of the arboviral encephalitides is the degree of contact between avian hosts and mosquito vectors. To analyze this interaction in detail, blood-fed mosquitoes that were confirmed vectors of eastern equine encephalomyelitis (EEE) virus were collected in 2002 from an enzootic site in central Alabama during the time this virus was actively transmitted. Avian-derived blood meals were identified to the species level of the host, and the proportion derived from each species was compared with the overall composition of the ...
Oral susceptibility of South African Culicoides species to live-attenuated serotype-specific vaccine strains of African horse sickness virus (AHSV). The oral susceptibility of livestock-associated South African Culicoides midges (Diptera: Ceratopogonidae) to infection with the tissue culture-attenuated vaccine strains of African horse sickness virus (AHSV) currently in use is reported. Field-collected Culicoides were fed on horse blood-virus mixtures each containing one of the seven serotype-specific vaccine strains of AHSV, namely serotypes 1, 2, 3, 4, 6, 7 and 8. The mean titres of virus in the bloodmeals for the seven vaccine strains were between 6.8 and 7.6 log10TCID50/mL. All females (n = 3262) that survived 10 days extrinsic incubati...
Acquired resistance of horses to Amblyomma cajennense (Fabricius, 1787) ticks. Acquired immunity of horses to larvae, nymphs and adults of the Amblyomma cajennense tick was evaluated through three consecutive experimental infestations of tick-bite naïve hosts. Data from these infestations were compared to those from field-sensitized horses and donkeys. It was observed that tick-bite naïve horses developed a low level of resistance after two infestations as shown by a significant decrease in larval yield and a tendency for lower engorged weight of nymphs during third infestation. Ticks fed on field-sensitized horses had a similar biological performance to that observed ...
Recent advances in molecular epidemiology and detection of Taylorella equigenitalis associated with contagious equine metritis (CEM). In the present review article, recent molecular advances relating to studies with Taylorella equigenitalis, as well as the recently described second species of the genus Taylorella, namely Taylorella asinigenitalis, have been described. Molecular genotyping of T. equigenitalis strains by pulsed-field gel electrophoresis (PFGE) after digestion with the suitable restriction enzyme(s) enabled the effective discrimination of strains, thus allowing the examination of the scientific mechanism(s) for its occurrence and transmission of contagious equine metritis (CEM). Alternatively, polymerase chain ...
Digenetic trematodes, Acanthatrium sp. and Lecithodendrium sp., as vectors of Neorickettsia risticii, the agent of Potomac horse fever. Neorickettsia (formerly Ehrlichia) risticii, the agent of Potomac horse fever (PHF), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. Insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. To determine the definitive helminth vector, five bats (Myotis yumanensis) and three swallows (Hirundo rustica, Tachycineta bicolor) were collected from a PHF endemic location in northern California. Bats and swallows were dissected and their major organs examined for trematodes and for N. risticii DNA...
Lateral transmission of equine arteritis virus among Lipizzaner stallions in South Africa. A serological study conducted in 1995 revealed that 7 stallions at the Lipizzaner Centre, Gauteng, South Africa, were seropositive for antibody to equine arteritis virus (EAV). A Lipizzaner stallion imported into South Africa from Yugoslavia in 1981 had previously (1988) been confirmed to be an EAV carrier. Despite being placed under life-long breeding quarantine, EAV had been transmitted between stallions at the Lipizzaner Centre. Objective: To investigate the phylogenetic relationships between the strain of EAV shed in the semen of the original carrier stallion and strains recovered from the...
Small-world topology of UK racing: the potential for rapid spread of infectious agents. The topology of the network of contacts between individuals has important effects on infectious disease dynamics within a population. Here we examine for the first time a network of contacts between training yards that occurred through racing. Objective: To explore the topology of this network and to consider the effects of the network on the potential for disease transmission. Methods: Race data from one week was analysed. Contacts were defined as occurring between trainers that raced horses in the same race and hence one trainer could contact another trainer several times. A connection was s...
Case-control study of factors associated with fibrinous pericarditis among horses in central Kentucky during spring 2001. To identify factors significantly associated with an epidemic of fibrinous pericarditis during spring 2001 among horses in central Kentucky. Methods: Case-control study. Methods: 38 horses with fibrinous pericarditis and 30 control horses examined for other reasons. Methods: A questionnaire was developed to solicit information regarding a wide range of management practices and environmental exposures from farm owners or managers. Results: The following factors were found in bivariate analyses to be significantly associated with an increased risk of pericarditis: being from a farm with mares an...
Surveillance results from the first West Nile virus transmission season in Florida, 2001. After West Nile virus (WNV) was first detected in Florida in July 2001, intensive surveillance efforts over the following five months uncovered virus activity in 65 of the state's 67 counties with 1,106 wild birds, 492 horses, 194 sentinel chickens, and 12 people found infected with the virus. Thirteen of 28 mosquito isolations came from Culex mosquitoes. As seen in the northeastern United States, wild bird mortality was the most sensitive surveillance method. However, unlike the predominantly urban 1999 and 2000 epizootics, the Florida transmission foci were rural with most activity detected ...
Risk factors for fecal shedding of Salmonella from horses in a veterinary teaching hospital. Identification of risk factors for horses shedding Salmonella in their feces helps identify patients at-risk of infection and protect the overall population through heightened biosecurity. Fecal samples from 230 hospitalized horses were cultured for Salmonella spp. Historical data were collected on 21 putative risk factors and assessed for association with the risk of a horse being culture positive using forwards stepwise logistic regression. Salmonella was isolated from 13 horses--most commonly from either the first (n=5) or second (n=4) sample collected. Only presenting complaint (confounded...
Evidence for a new field Culicoides vector of African horse sickness in South Africa. Between February and May 1998, approximately 100 horses died of African horse sickness (AHS) in the cooler, mountainous, central region of South Africa. On 14 affected farms, 156,875 Culicoides of 27 species were captured. C. imicola Kieffer, hitherto considered the only field vector for AHS virus (AHSV), constituted <1% of the total Culicoides captured, and was not found on 29% of the farms. In contrast, 65% of the Culicoides were C. bolitinos Meiswinkel, and was found on all farms. Five isolations of AHSV were made from C. bolitinos, and none from 18 other species of Culicoides (including C....
