Objective—To determine signalment, history, clinical
signs, duration, seasonality, and response to various
treatments reported by owners for headshaking in
Animals—109 horses with headshaking.
Procedure—Owners of affected horses completed a
Results—78 affected horses were geldings, 29 were
mares, and 2 were stallions. Mean age of onset was
9 years. Headshaking in 64 horses had a seasonal
component, and for most horses, headshaking began
in spring and ceased in late summer or fall. The most
common clinical signs were shaking the head in a vertical
plane, acting like an insect was flying up the nostril,
snorting excessively, rubbing the muzzle on
objects, having an anxious expression while headshaking,
worsening of clinical signs with exposure to
sunlight, and improvement of clinical signs at night.
Treatment with antihistamines, nonsteroidal antiinflammatory
drugs, corticosteroids, antimicrobials,
fly control, chiropractic, and acupuncture had limited
success. Sixty-one horses had been treated with
cyproheptadine; 43 had moderate to substantial
Conclusions and Clinical Relevance—Headshaking
may have many causes. A large subset of horses have
similar clinical signs including shaking the head in a
vertical plane, acting as if an insect were flying up the
nostrils, and rubbing the muzzle on objects.
Seasonality and worsening of clinical signs with exposure
to light are also common features of this syndrome.
Geldings and Thoroughbreds appear to be
overrepresented. Cyproheptadine treatment was beneficial
in more than two thirds of treated horses. (J
Am Vet Med Assoc 2001;219:334–337)
Objective—To assess spatial and temporal patterns
of seroprevalence among dogs in California to the
causative agent of granulocytic ehrlichiosis (GE).
Sample Population—Sera of 1,082 clinically normal
dogs from 54 of 59 counties in California in 1997 to
Procedure—Serum-specific IgG reactivity to
Ehrlichia equi was assessed by use of an immunofluorescent
antibody assay, using E equi-infected horse
neutrophils as substrate. Data were analyzed, using a
geographic information system. Spatial analysis of
seroprevalence included first order Bayesian analysis
of seroprevalence and second order analysis of clustering
by K-function and Cuzick-Edwards tests.
Monthly seroprevalence among dogs was examined
by use of regression on monthly densities of Ixodes
pacificus adults and nymphs .
Results—Seroprevalence among dogs to E equi was
8.68%. Data were seasonally bimodal with highest
prevalence in winter (when adult ticks were abundant)
and a secondary peak in late spring (corresponding to
nymphal ticks). Humboldt County had the highest seroprevalence
(47.3%), and other northern coast range
counties had seroprevalence from 15 to 30%.
Conclusion and Clinical Relevance—The patchy
distribution of exposure to Ehrlichia organisms is a
subset of the distribution of the tick vector. This may
reflect enzootic cycles or climatic or historical factors
that limited the range of the disease. Dogs, horses,
and humans from north coast range counties in
California are at increased risk of GE. These data provide
a background for assessing risk of infection in
horses and dogs, depending on geographic location.
Dogs may be sentinels for assessing risk of GE in
humans. (Am J Vet Res 2001;62:1599–1605)
Objective—To describe clinical and clinicopathologic findings and outcome of horses with meningitis and meningoencephalomyelitis.
Design—Retrospective case series.
Procedures—Medical records of horses admitted to the hospital during a 25-year period were reviewed. Horses with a definitive diagnosis of meningitis or meningoencephalomyelitis were included in this study. Information extracted from the medical records included signalment, history, reason for admission, clinical signs, results of clinicopathologic testing and diagnostic procedures, treatment, outcome, and necropsy findings.
Results—22 horses had confirmed infectious disease (19 bacterial, 2 parasitic, and 1 fungal), 4 had suspected infectious disease on the basis of CSF cytologic examination findings, and 2 had noninfectious meningitis or meningoencephalomyelitis. Trauma of the head and vertebral column with disruption of the blood-brain barrier and local ascending or hematogenous spread were the most common routes of infection. Common neurologic signs included abnormal mental status, cranial nerve deficits, vestibular dysfunction, ataxia, tetraparesis, and apparent neck pain. Common hematologic abnormalities included leukocytosis, neutrophilia, lymphopenia, and hyperfibrinogenemia. Cytologic examination of CSF samples revealed moderate to marked suppurative inflammation. Mortality rate was 96.4%. Microbial culture of CSF yielded bacterial growth in 15 of 23 horses (before death [2 horses], after death , and both ).
Conclusions and Clinical Relevance—Results suggested that meningitis and meningoencephalomyelitis are uncommon disorders in horses. Infectious disease was more common than noninfectious disease. Local trauma, ascending infection, or hematogenous spread of infection were the most common causes of meningitis or meningoencephalomyelitis. Neurologic deficits, neutrophilia, lymphopenia, hyperfibrinogenemia, and CSF with neutrophilic pleocytosis were common findings in affected horses.
Objective—To determine susceptibility of cattle to
infection with Ehrlichia equi and the agent of human
granulocytic ehrlichiosis (HGE).
Design—Experimental disease and prevalence survey.
Animals—6 cattle, 2 horses, and 2,725 serum samples
from healthy cattle.
Procedure—2 cattle and 1 horse were inoculated
with E equi, 2 cattle and 1 horse were inoculated with
the HGE agent, and 2 cattle served as sham-inoculated
controls; inoculated animals were evaluated via
clinical, hematologic, serologic, and real-time polymerase
chain reaction tests. Prevalence of antibodies
against E equi in 2,725 healthy cattle was determined
by use of an indirect immunofluorescent technique.
Results—No abnormal clinical or hematologic findings
or inclusion bodies within granulocytes were
observed in the cattle after inoculation, and results of
all polymerase chain reaction tests were negative.
Seroconversion in inoculated cattle developed 10 to
12 days after inoculation (reciprocal titers, 160). Both
horses developed clinical signs of ehrlichiosis. Five of
2,725 (0.18%) cattle were seropositive for E equi,
with titers ranging from 20 to 80. All seropositive cattle
originated from the same tick-rich region in the
Sierra Nevada foothills.
Conclusions and Clinical Relevance—Results suggest
that cattle are not susceptible to infection with E
equi or the agent of HGE and that prevalence of exposure
to E equi in healthy cattle is low. Therefore, E
equi and the agent of HGE are likely of negligible
importance for cattle in North America. (J Am Vet Med
Objective—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.
Sample Population—2,621 flies of various species.
Procedure—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 horses is endemic. Three of the 5 farms
(which housed a total of 358 horses) had diseased
horses during the study period. A total of 2,621 flies
of various species were tested for the PLD gene of C
Results—Evidence of bacterial DNA for the PLD
gene was detected in skin biopsy specimens from
clinically affected horses and from 3 fly species collected
from farms where affected horses were
housed. Farms with a high incidence of diseased
horses had a high proportion of insects carrying the
organism. High percentages of flies with positive
results for the PLD gene were observed in October,
when most clinically affected horses were observed.
Conclusions and Clinical Relevance—Our results
are consistent with the hypothesis that C pseudotuberculosis
may be vectored to horses by flies. Three
potential vectors were identified, including
Haematobia irritans, Stomoxys calcitrans, and Musca
domestica. The organism can be identified in up to
20% of house flies (Musca domestica) in the vicinity
of diseased horses. (Am J Vet Res 2004;65:829–834)
Objective—To determine clinical, laboratory analysis, and necropsy findings for equids with oleander toxicosis and to identify factors associated with outcome.
Design—Retrospective case series.
Procedures—Medical records of equids with detectable concentrations of oleandrin in serum, plasma, urine, or gastrointestinal fluid samples and equids that had not received cardiac glycoside drugs but had detectable concentrations of digoxin in serum were identified via a medical records database search. Descriptive statistics were calculated for medical history, physical examination, laboratory analysis, and necropsy variables. Logistic regression analysis was used to identify physical examination and laboratory analysis factors significantly associated with outcome.
Results—3 of 30 (10.0%) equids died before or immediately after arrival at the hospital. Of the other 27 equids, 23 (85.2%) had gastrointestinal tract abnormalities, azotemia was detected for 19 (70.4%), and a cardiac arrhythmia was ausculted for 18 (66.7%). Mortality rate for all equids was 50.0%; mortality rate for hospitalized equids was 44.4%. The most common cause of death was cardiac dysfunction. Odds of survival to discharge from the hospital were lower for equids with cardiac arrhythmias versus those without arrhythmias and decreased with increasing Hct and serum glucose concentrations. Odds of survival increased with increasing serum chloride concentration and duration of hospitalization.
Conclusions and Clinical Relevance—Equids with oleander toxicosis frequently had simultaneous gastrointestinal tract, cardiac, and renal problems. Oleander intoxication should be a differential diagnosis for equids with colic in geographic areas where oleander is found, especially when azotemia or cardiac arrhythmias are detected concurrently.
Objective—To determine molecular characteristics, antimicrobial susceptibility, and toxigenicity of Clostridium difficile isolates from horses in an intensive care unit and evaluate associations among severity of clinical disease with specific strains of C difficile.
Procedures—Feces were collected from horses admitted for acute gastrointestinal tract disease with loose feces and submitted for microbial culture and immunoassay for toxin production. Polymerase chain reaction assays were performed on isolates for toxins A and B genes and strain identification.
Results—Isolates were grouped into 3 strains (A, B, and C) on the basis of molecular banding patterns. Toxins A and B gene sequences were detected in 93%, 95%, and 73% of isolates of strains A, B, and C, respectively. Results of fecal immunoassays for toxin A were positive in 40%, 63%, and 16% of horses with strains A, B, and C, respectively. Isolates in strain B were resistant to metronidazole. Horses infected with strain B were 10 times as likely to have been treated with metronidazole prior to the onset of diarrhea as horses infected with other strains. Duration from onset of diarrhea to discharge (among survivors) was longer, systemic inflammatory response syndromes were more pronounced, and mortality rate was higher in horses infected with strain B than those infected with strains A and C combined.
Conclusions and Clinical Relevance—Horses may be infected with a number of heterogeneous isolates of C difficile. Results indicated that toxigenicity and antimicrobial susceptibility of isolates vary and that metronidazole-resistant strains may be associated with severe disease.
Case Description—A 15-year-old Saddlebred gelding used for competitive pleasure driving had a 1-year history of head shaking while pulling a cart.
Clinical Findings—The horse had cystic corpora nigra in both eyes and concomitant classic and operant conditioned responses to wearing a bridle with bilateral eye covers (blinkers).
Treatment and Outcome—Deflation and coagulation of the cysts with an infrared diode laser and behavior modification consisting of desensitization and counterconditioning were used to successfully restore performance.
Clinical Relevance—Behavioral changes in horses can result from a combination of physical and psychologic causes. A combination of appropriate medical treatment of physical abnormalities and a behavioral modification plan is necessary to successfully treat behavioral problems in these patients.
Objective—To evaluate deafness in American Paint Horses by phenotype, clinical findings, brainstem auditory-evoked responses (BAERs), and endothelin B receptor (EDNBR) genotype.
Design—Case series and case-control studies.
Animals—14 deaf American Paint Horses, 20 suspected-deaf American Paint Horses, and 13 nondeaf American Paint Horses and Pintos.
Procedures—Horses were categorized on the basis of coat color pattern and eye color. Testing for the EDNBR gene mutation (associated with overo lethal white foal syndrome) and BAERs was performed. Additional clinical findings were obtained from medical records.
Results—All 14 deaf horses had loss of all BAER waveforms consistent with complete deafness. Most horses had the splashed white or splashed white–frame blend coat pattern. Other patterns included frame overo and tovero. All of the deaf horses had extensive head and limb white markings, although the amount of white on the neck and trunk varied widely. All horses had at least 1 partially heterochromic iris, and most had 2 blue eyes. Ninety-one percent (31/34) of deaf and suspected-deaf horses had the EDNBR gene mutation. Deaf and suspected-deaf horses were used successfully for various performance events. All nondeaf horses had unremarkable BAER results.
Conclusions and Clinical Relevance—Veterinarians should be aware of deafness among American Paint Horses, particularly those with a splashed white or frame overo coat color pattern, blend of these patterns, or tovero pattern. Horses with extensive head and limb markings and those with blue eyes appeared to be at particular risk.
Objective—To determine molecular characteristics of
Clostridium difficile isolates from foals with diarrhea
and identify clinical abnormalities in affected foals.
Animals—28 foals with C difficile-associated diarrhea.
Procedure—Toxigenicity, molecular fingerprinting,
and antibiotic susceptibility patterns were determined.
Information on signalment, clinical findings,
results of clinicopathologic testing, whether antimicrobials
had been administered prior to development
of diarrhea, and outcome was obtained from the
Results—Twenty-three (82%) foals survived. Toxin
A and B gene sequences were detected in isolates
from 24 of 27 foals, whereas the toxin B gene alone
was detected in the isolate from 1 foal. Results of
an ELISA for toxin A were positive for fecal samples
from only 8 of 20 (40%) foals. Ten of 23 (43%) isolates
were resistant to metronidazole. Molecular
fingerprinting revealed marked heterogeneity
among isolates, except for the metronidazole-resistant
isolates. Sixteen foals had tachypnea.
Hematologic abnormalities were indicative of
inflammation. Common serum biochemical abnormalities
included metabolic acidosis, hyponatremia,
hypocalcemia, azotemia, hypoproteinemia, hyperglycemia,
and high enzyme activities. Passive transfer
of maternal antibodies was adequate in all 12
Conclusions and Clinical Relevance—Results suggest
that a large percentage of C difficile isolates
from foals with diarrhea will have the toxin A and B
gene sequences. Because of the possibility that isolates
will be resistant to metronidazole, susceptibility
testing is warranted. Clostridium difficile isolates
from foals may have a substantial amount of molecular
heterogeneity. Clinical and hematologic findings in
affected foals are similar to those for foals with diarrhea
caused by other pathogens. (J Am Vet Med