Equine Pathogens Flashcards
African Horse Sickness
viral respiratory disease of horses but signs are primarily pulmonary. Transmitted by insects, primarily Culicoides. Clinical signs typically develop 5-7 days after infection and begin with fever and conjunctivitis. Some may recover, but many go on to develop the pulmonary and/or cardiac forms of AHS. The pulmonary form consists of acute respiratory distress, coughing, sweating, and foaming from the nostrils; this form is usually fatal. The cardiac form consists of edema of the head and neck as well as abdominal pain and depression. A characteristic sign is swelling in the indentation above the eyes (also referred to as swelling of the supraorbital fossa). About 50% of animals with the cardiac from die fo heart failure while the rest gradually recover after about one week.
Anaplasma phagocytophilum
Equine Granulocytic Ehrlichiosis (formerly Ehrlichi equi)- clinical signs: fever, lethargy, tachycardia and limb edema. Microscopic observation of a morula within the neutrophil. Diagnosis can be supported via PCR assay. Spread via tick bites. Treat with oxytetracyline.
Anhidrosis
The inability to sweat, which can be fatal if not addressed. The cause is unknown. It tends to occur in hot humid climates and may occur in horses raised in the climate or, more commonly, horses brought into the climate. The most successful treatment is to move the horse back to a more favorable climate.
Anoplocephala magna
tapeworm of horse; usually found in the small intestine
Treat with pyrantel salts
involves free-living oribatid mites as intermediate hosts
Anoplocephala perfoliata
tapeworm of horse; usually found in the ileocecal junction
Treat with pyrantel salts
involves free-living oribatid mites as intermediate hosts
Auriculppalpebral nerve block
Disrupts motor to orbiculoris oculi
Bog spavin
fluid distension of the high mobility joint in the hock called the tibiotarsal or tarsocrural joint
Bone spavin
bony growth within the lower hock joint of horse or cattle. It is caused by osteoarthritis, and the degree of lameness that results can be serious enough to end a horse’s competitive career
Borrelia burgdorferi
Lyme Disease
low-grade fever, stiffness and lameness in more than one limb, muscle tenderness, hyperesthesia, swollen joints, lethargy and behavioral changes
oxytetracycline of doxycycline
Burkholderia mallei
Glanders - can be identified on smears make from fresh lesions as mainly extracellular straight gram-negative rods with rounded ends. Diagnostic tests: PCR, ELISA, and western blot but mostly need to know that are used in international trade are complement fixation (CF) serology and the mallein test. Mallein test is considered the most reliable, sensitive and specific. It involves injection of mallein purifies protein derivative intradermally into the lower eyelid. The test is read 24 to 48 hours and a positive reaction is characterized by edematous swelling or purulent discharge. Horse should not be treated; local authorities should be notified if a case is suspected and if disease is confirmed, horses must be humanely destroyed and affected carcasses should be burned and buried. Endemic in regions of the Middle East, Africa, and South America. Affects donkeys, mules, and small ruminants. Horses can become chronic or occult carriers and shed this deadly and potentially zoonotic pathogen.
Buttress foot
also known as pyramidal disease or extensor process disease, arises secondary to excessive strain on the extensor process of P3 resulting in periostitis in the region of the pyramidal process. There is often associated fracture of the process. As the disease progresses, lameness worsens and skin of the cornet band becomes thickened and indurated. In addition, the wall of the hoof protrudes at the toe.
C. pseudotuberculosis test
internal abscesses, hemagglutination inhibition test
Cerebellar Abiotrophy
usually observed in foals which are less than one year of age, particularly 1-6 months of age. It is mostly seen in Arabian, Oldenburg, and Gotland breeds. There is no treatment and signs may be progressive. Diagnosis is based on a good history and clinical signs such as intention tremors, lack of a menace, hypermetria, and ataxia.
Cervical vertebral malformations (Wobbler Syndrome)
Seen primarily in horses under a year of age
Chorioptes equi
mange mite that is usually found around the foot and fetlock. It causes pruritic dermatitis that can cause the formation fo papules, crusts, thickened skin, as well as alopecia. The mites are often found in feathered hair around the fetlock of draft horse. Ivermectin is the treatment of choice.
Chronic hepatitis histopathology
hepatocyte, damage, variable fibrosis, inflammatory infiltration, and evidence of biliary hyperplasia with bile stasis
Chronic seborrheic dermatitis
“scratches” due to wet environment
Club foot
Condition seen in horses secondary to contracture of the distal interphalangeal joint leading to steep hoof wall and shortened toe.
Coggin’s test
EIA - effective in diagnosing infection in chronic asymptomatic carriers, immunodiffusion
Common IM vaccine reaction
Strangles vaccine is associated with a soft tissue reaction, there is now an intra-nasal vaccine available with local protection
Commonly injured when horse flips over backwards
Ruptured longus capitis
Corynebacterium pseudotuberculosis
“Pigeon fever” Causes ulcerative lymphangitis and abscesses in the pectoral region of horses. Treatment is aimed at hot packing the swellings and draining the abscesses. Antibiotic can be administered but have been known to prolong the disease by delay abscess formation.
Culicoides
“sweet itch” Diffuse lesions, recurs seasonally in the warmer months and tends to worsen with age. Occurs due to an allergy to the saliva of the gnat. Pruritic and develop lesions on the poll, mane, and tail from self-trauma, ventral midline dermatitis can occur as well. Decrease exposure to gnats and treat with steroids.
Cutaneous glanders
Also known as Farcy. The cutaneous form develops over several months, beginning with cough and dyspnea as well. Eventually nodules develop in subcutaneous tissue along the course of the lymphatics of the legs, costal areas, and ventrum. They can rupture and excrete infectious purulent exudate. Infected lymphatics may form thickened cord-like lesions that sometimes coalesce into a string of beads appearance know as “farcy pipes.” Nodular lesions of other organs may also be found.
Dandy-Walker syndrome
Rare condition seen in Arabians and Thoroughbred foals which results in a midline defect of the cerebellum and cystic dilation of the four ventricle.
Degenerative myeloencephalopathy
Seen primarily in horses under a year of age, causes a symmetrical ataxia.
Dermatophilus congolensis
gram positive, non-acid fast, facultative anaerobic actinomycete. Causes crusting dermatitis in large animals when there is high moisture on the skin as well as mechanical irritation. Horses with long, wet haircoats are often affected. Lesions are commonly on the dorsum and pasterns of horses and are classically described as “paintbrush” lesions. Can be diagnosed with a direct smear preparation. Treatment includes keeping the haircoat clean and dry and penicillins if the lesions are severe. Lesions typically heal rapidly.
“mud fever” - gram positive branching bacteria Enters skin that is damaged by wetness and causes suppurative crusts, usually along dorsum of horse.
Dermatphytosis
Crusting dermal lesions
KOH test
DIC coagulation parameters
Prolongation of the prothrombin time (PT) and the activated partial thromboplastin time (aPTT) reflect the underlying consumption and impaired synthesis of the coagulation cascade.
Fibrinogen level has initially thought to be useful in the diagnosis of DIC but because it is an acute phase reactant, it will be elevated due to the underlying inflammatory condition. Therefore, a normal (or even elevated) level can occur in over 57% of cases. A low level, however, is more consistent with the consumptive process of DIC.
A rapidly declining platelet count
High levels of fibrin degradation products, including D-dimer, are found owing to the intense fibrinolytic activity stimulated by the presence of fibrin in the circulation.
The peripheral blood smear may show fragmented red blood cells (known as schistocytes) due to shear stress from thrombi. However, this finding is neither sensitive nor specific for DIC
Dictyocaulus arnfeldi
Lungworm; donkey definitive host - Baerman test
Dourine
“covering sickness” trypanosomal (protozoa) venereal disease
notifiable, causes paralysis
Can only treat symptoms, no cure and no vaccination
50% mortality
Draschia megastoma
migrating parasite that can cause focal granulomas in the lung
Dry matter protein intake requirement
12%
Eastern Equine Encephalomylitis (EEE)
Arbovirus with zoonotic potential - “sleeping sickness”
transmitted by mosquitos
mortality can be as high at 90%
Ehrlichi equi
neutrophil, Equine Granulocytic Ehrilichiosis, lethargy, anorexia, fever, limb edema and hematology changes such as neutropenia and thrombocytopenia.
Ehrlichia risticii
Potomac Horse Fever: lethargy, anorexia, fever, diarrhea (in less that 60% of cases) and laminitis. Diagnosis requires measurement of paired serum titer via immuno-flourescent antibodies or detection of the organism via PCR in the blood or feces.
Enterolith in California
Magnesium ammonium phosphate due to alfalfa in California
EPM treatment
Ponazuril, Nitazoxanide, folate inhibitors (Sulfadiazine, pyrimethamine)
Equine Adenovirus
Normally found in the upper respiratory tract of the horse, but can cause a lower respiratory tract infection in immunocompromised individuals, particularly foals with those town conditions, leading to an often fatal pneumonia.
Equine Degenerative Myeloencephalopathy
Associated with a deficiency in Vitamin E. CLincial signs are usually in the form of a wide-based stance, conscious proprioceptive deficits, ataxia, paresis, and spasticity, which is worse in the hindlimbs.
Equine Eosinophilic Granuloma
The lesions are nodular, nonulcerative, and nonpruritic. They often are found in the saddle, central truncal, and lateral cervical areas and may have a gray-white central core. Older lesions may become mineralized. Both insect bites and trauma have been suggested as causes, although the occasional onset during winter in cold climates and in noncontact saddle or tack areas suggests multifactorial causes
Equine Granulocytic Ehrlichiosis
tick-borne
infectious, noncontagious, seasonal disease
rickettsial agent Anaplasma phagocytophilum
Signs may be mild. Horses <1 yr old may have a fever only; horses 1–3 yr old develop fever, depression, mild limb edema, and ataxia. Adults exhibit the characteristic signs of fever, partial anorexia, depression, reluctance to move, limb edema, petechiation, and icterus
Demonstration of the characteristic cytoplasmic inclusion bodies in a standard blood smear is diagnostic
Treat with Oxytetracycline
Equine Herpes Virus (AHV) Myeloencephalitis
Common clinical signs: bladder paralysis with urine dribbling, fecal retention, and hind limb ataxia. Xanthochromic CSF with the high protein and normal cell count also suggestive of EHV. Virus isolation can be attempted on buffy coat samples, nasal swabs, and/or CSF in an attempt to identify the virus.
Equine Herpes Virus 3
Causes papules, pustules, and ulcers to the vestibular mucosa, vulvar skin, and the penis and prepuce (balanoposthitis). Less frequently, it can involve the skin of the face. There are no systemic signs or consequences of the infection, although secondary bacterial infections are possible. Spontaneous recovery usually occurs over about 2 weeks, and no treatment is usually required except sexual rest to prevent spread as balanoposthitis is venereally transmitted.
Equine Protozoal Myeloenchephalitis (or myelitis) (EPM)
can be seen as any age and is caused by Sarcocystis neurona. It should be suspected when a horse has asymmetric neurological signs as it is a multifocal disease of the central nervous system. Clinical signs include hyporeflexia, spasticity, localized areas of sweating, cerebellar signs, head tilt. facial paralysis, circling, dysphagia, and blindness. This will result in damage of both white and gray matter.
Equine Viral Arteritis
Venereal or aerosol - Nidovirales
Typical cases are characterized by fever, depression, anorexia, leukopenia, dependent edema (especially of the lower hind extremities, scrotum, and prepuce in the stallion), conjunctivitis, supra- or periorbital edema, nasal discharge, respiratory distress, skin rash, temporary subfertility in affected stallions, abortion, and infrequently, illness and death in young foals
Symptomatic treatment
Fistulous withers
inflammation of the supraspinous bursa. This bursa is variable in size and location but is usually found between the second and fifth thoracic vertebrae and can extend ventrolaterally to the margin of the scapular cartilage. The etiology is thought to be infectious. Clinical signs are pain, heat, and swelling in the region of the bursa. After days to weeks, the bursa can rupture resulting in draining of fluid. Brucella abortus has been identified in up to 80% of clinical cases by serology and culture. Treatment consists of flushing the fistula and appropriate antibiotics.
Fluid calculation
(deficit x BW) + maint (60 ml/kg/day)
