equine infectious resp diseases Flashcards
what infectious diseases can cause resp disease in horses?
- equine influenza
- equine herpes 1 & 4
- equine viral arteritis - notifiable
- dictyocaulus arnfieldi (lung worm)
what is the transsmission and pathogenesis of equine influenza?
- Transmission: aerosol (& fomites)
◦ highly infectious, downwind 1 mile - Pathogenesis: Infection of respiratory epithelial cells (URT)
◦ nasopharyngeal virus shedding
◦ destroys cilia - seconday probles eg pneumonia
what is the diagnosis of equine influenza?
◦ Nasal swab - cover in a little bit of saline, as will not get as accurate results if has dried out
‣ Detection of viral antigen (ELISA)
‣ Detection of RNA (RT-PCR)
◦ Serum samples – detection of antibodies (serology)
‣ ELISA
‣ Haemagglutination inhibition (HI) - 4-fold increase in titre indicates seroconversion
for the convalescent sample (serology) - needs time to seroconvert
what is the clinical signs, treatment and prevention of equine influenza?
Clinical signs: Fever, cough and nasal discharge (serous, may become mucopurulent – secondary bacterial infection)
Treatment & prevention:
◦ Vaccines available -
‣ reduce severity of clinical sings, but can still get,
◦ Nursing care and anti-inflammatory medication (antibiotics for secondary infection)
what is the transmission and pathogenesis of equine herpes virus?
Transmission: inhalation of aerosol / contact with infected fomites / reactivation from latency
Pathogenesis:
◦ Infection of respiratory epithelial cells –> nasopharyngeal virus shedding
◦ white blood cells (cell-associated viraemia) –> dissemination to sites of secondary replication
‣ pregnant uterus –> abortion (rare)
‣ spinal cord –> neurological disease (rare)
◦ endothelial cells –> inflammation & thrombi
◦ latency established (reactivation during stress)
what is the clinical signs, treatment and prevention of equine herpes virus?
Clinical signs:
Common - Fever, occasional mild cough and slight nasal discharge, poor performance (age / immunity dependent)
Occasional - Abortion / sick neonatal foal, neurological disease (equine herpesvirus myeloencephalopathy EHM)
Treatment & prevention:
◦ Vaccines available - not widely vaccinated against - often stud animals
◦ Rest in athletic animals;
EHM: nursing care and anti-inflammatory medication.
what is the diagnosis of equine herpes virus?
◦ Nasal swab (and placenta / fetus) - Viral DNA - PCR
◦ Blood samples
‣ Virus isolation in tissue culture (anti-coagulated blood - acute)
‣ Detection of antibodies by complement fixation test (serum)
- if a horse has just aborted then can’t take blood sample as the horse would not had had time to seroconvert, so need to send off nasal swab and aborted material
what different presentation fo disease do the different seroytpes of equine herpes virus cause?
EHV 1 - neutrotrohic disease
EHV 1 but also 4 - abortion
EHV 1 & 4 - resp disease
what is the transmission and pathogenessis of equine viral arteritis ?
Transmission: Respiratory, venereal, and congenital routes or by indirect means (fomites)
Pathogenicity:
◦ Invades upper and lower respiratory tract. Infected monocytes and T lymphocytes transport EAV to the regional lymph nodes (e.g. bronchial), where it undergoes a further cycle of replication before being released into the bloodstream (cell-associated viraemia).
‣ 10–70% of stallions become persistently infected – carrier stallions may shed virus in their semen.
‣ Can cause abortion in pregnant mares.
what are the clinical signs, treatment and prevention of equine arteritis?
Clinical signs:
◦ Often asymptomatic, fever, nasal discharge, loss of appetite, respiratory distress, skin rash, muscle soreness, conjunctivitis, and depression.
Treatment & prevention:
◦ General supportive care during the acute phase of infection.
◦ There is no treatment to eliminate persistent infection in stallions. - don’t bred from them
◦ Inactivated virus vaccine [is available]. - not commonly vaccinated against in the UK
what are the diagnostic techniques for equine viral arteritis?
Diagnostic tests:
◦ Virus detection in body secretions or fluids, whole blood, or tissues by virus isolation, RT-PCR and in situ hybridization
◦ Identification of viral antigen in tissues
◦ Detection of viral-specific antibodies by serology.
◦ ELISA used for routine screening of horses that show no clinical signs of infection, e.g. for pre-breeding or sales requirements.
what is the trasnmission and pathogenesis of dictyocaulus arnfieldi?
Transmission:
Ingestion of L3 larvae from faeces / pasture. Donkeys are main source of pasture contamination.
Pilobolus fungi involved in dissemination?
Pathogenesis:
Mucopurulent exudate, hyperplastic epithelium, lymphocytic infiltrate in lamina propria (alveolitis, bronchiolitis, bronchitis). Raised areas of over-inflated pulmonary tissue
what are the clinical signs of dictyocaulus arnfieldi?
present similarly to equine asthma - increased expiratory effort as trying to push air out of hyperplastic bronchi
Clinical signs - Moderate–severe coughing (exercise), mucopurulent discharge
what is the treatment and diagnosis of dictyocaulus arnfieldi?
Treatment - Antiparasitic drugs (esp. moxidectin and ivermectin) – need to bring indoors to treat or move onto clean pasture
Diagnosis:
* First-stage larvae L1 in faeces (infrequent & few)
* Tracheal wash for eggs, larvae & WBCs
* [failure of antibiotic therapy, season, history]
what is the acronym and what does it stand for, for the controle of outbreaks of resp diseases?
hwhar are the other control stratergies for outbreaks and what are the hurdles to controlling outbreakes?
DISH
* Disinfection - effective products, how to disinfect
* Isolation - is it effective and correct isolation
* Submission (samples for diagnosis)
* Hygienic procedures
Vaccination in the face of an outbreak
Common hurdles
* Slow identification of affected horses
* Delay in diagnostic test results
* Owner compliance
* Declaration of end of outbreak?
