Infectious Flashcards
Is EHV-1 an enveloped or non-enveloped virus?
What environmental conditions are unfavorable for the virus?
EHV-1 has a viral envelope which must remain intact for its environmental survival, transmission and infection. It is susceptible to many commonly used disinfectants as well as environmental conditions such as air temperature, desiccation and UV light.
Potentially infectious EHV-1 persists in the environment
for at least 48 hours (wood shavings ++) and for up to 14 days in water.
Environmental persistence of equid herpesvirus type-1
evj 2021
Updated ACVIM consensus statement on equine herpesvirus-1
jvim 2024
Are horses genetically predisposed to equine herpesvirus myeloencephalopathy?
The results exclude the involvement of a recessive genetic factor in the susceptibility to develop clinically apparent EHM.
Genome-wide association study for host genetic factors associated with equine herpesvirus type-1 induced myeloencephalopathy
evj 2020
Which assertion is true concerning the detection of EHV-1 in urine samples of EHM horses?
A- DNA presence in urine for longer duration and with higher concentration than buffy coat
B- DNA presence in urine for longer duration and with higher concentration than nasal swab
C- DNA presence in urine was similar in duration and concentration than nasal swab
D- DNA presence in urine was similar in duration and concentration than buffy coat
Answer A
Urine vs buffy coat → DNA presence was detected in urine samples for longer duration and with slightly higher concentration.
Urine vs nasal swab → detection of EHV-1 in urine was similar in duration with lower DNA concentrations.
Detection of equine herpesvirus-1 (EHV-1) in urine samples during outbreaks of equine herpesvirus myeloencephalopathy
evj 2024
What is the best sampling technique to detect EHV-1 infection? (depending on the outbreaks)
- When possible, it is advisable to test both nasal secretions and blood for the presence of EHV-1 but when resources are limited or large numbers of horses have to be tested then only nasal secretions should be tested.
- The exception is in mares after abortion when blood samples are more sensitive than nasal secretions.
Viremia and nasal shedding for the diagnosis of equine herpesvirus-1 infection in domesticated horses
jvim 2024
Updated ACVIM consensus statement on equine herpesvirus-1
jvim 2024
What are the negative prognostic factors for a return to sport in horses with EHM? (several answer)
- Urinary complications
- Vascular complications (vasculitis)
- Ataxia grade ≧ 4/5
- Ataxia grade ≧ 3/5
- Lymphopenia
- Neutrophilia
- Neuropathogenic genotype
- Horses with an ataxia grade at admission ≥4/5 had an increased fatality rate and 10% chance of reaching their preoutbreak performance level.
- None of the horses with both vascular and urinary complications returned to their previous performance level.
- Overall, horses affected by EHM had 68% chance of returning to exercise.
Long-term performance of show-jumping horses and relationship with severity of ataxia and complications associated with myeloencephalopathy caused by equine herpes virus-1
jvim 2024
A 14-year-old Quarter Horse presents with fever, lethargy, limb edema, and severe muscle pain. Laboratory findings show significantly elevated CK and AST levels. Neurologic examination reveals diffuse proprioceptive ataxia. What is the most likely diagnosis and initial management strategy?
A) Anaplasma phagocytophilum infection; treat with tetracyclines and corticosteroids.
B) Equine herpesvirus myeloencephalopathy; administer antivirals and supportive care.
C) Polysaccharide storage myopathy; initiate dietary management and vitamin E supplementation.
D) Hyperkalemic periodic paralysis; administer potassium-free fluids and manage with diet.
Correct answer: A
Justification: The combination of fever, muscle disease with elevated CK/AST, and neurologic symptoms (ataxia) in a Quarter Horse suggests Anaplasma phagocytophilum infection, especially given the MYHM association with severe muscle disease in QH breeds. Treatment with tetracyclines is recommended, along with corticosteroids for immune-mediated myositis.
2023 Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease
A group of healthy horses received a combined equine influenza virus (EIV) and equine herpesvirus (EHV-1) vaccine. One subgroup was treated with a single intravenous dose of dexamethasone, while another subgroup received three doses over 72 hours. What is the likely outcome regarding their antibody response to EIV and EHV-1?
A) Both groups will have significantly lower antibody titers against EIV and EHV-1 compared to the control group.
B) Only the group receiving multiple dexamethasone doses will have reduced antibody titers against EIV.
C) Both groups will show no change in antibody titers against EIV but a decrease in EHV-1 titers.
D) Antibody titers will not be affected by dexamethasone in any of the groups.
Correct answer: B
Justification: The study found that horses receiving multiple doses of dexamethasone did not show a significant increase in EIV antibody titers, while horses receiving a single dose did show an increased response. Dexamethasone did not significantly affect antibody titers against EHV-1.
Effect of dexamethasone on antibody response of horses to vaccination with a combined equine influenza virus and equine herpesvirus-1 vaccine. 2023
What is one of the key limitations of the currently available African horse sickness (AHS) vaccines?
A) They are too expensive to produce.
B) They do not prevent the spread of the virus.
C) They may cause disease through reversion to virulence.
D) They are not available in endemic regions.
C) They may cause disease through reversion to virulence: live attenuated viruses, can revert to virulence or cause reassortment, posing a risk.
JUSTIFICTION:
A) They are too expensive to produce: NO. The study does not mention high production costs as a key limitation of current AHS vaccines. (US$3.5 million: represents the estimated investment needed to bring a new AHS vaccine to market VS US$95 million: the annual economic impact of AHS affecting endemic regions.)
B) They do not prevent the spread of the virus: NO. The vaccines do help prevent the spread, but concerns revolve around their safety and effectiveness in global trade.
D) They are not available in endemic regions: NO. The vaccines are available in endemic regions such as South Africa, Ethiopia, and Senegal, though they have technical limitations.
Economic assessment of African horse sickness vaccine impact 2021 EVJ
What is the main challenge associated with using live attenuated vaccines (LAV) for controlling African horse sickness (AHS), and how could DIVA vaccines address this issue?
A) The high cost of producing LAV
B) The inability to differentiate vaccinated horses from naturally infected ones, which DIVA vaccines could resolve
C) The low efficacy of LAV in preventing AHS, whereas DIVA vaccines offer better protection
D) LAV vaccines are not available in Southeast Asia, but DIVA vaccines are widely used
B) correct. The main limitation of LAV vaccines is that they induce an immune response to all virus antigens, making it hard to differentiate between vaccinated and naturally infected horses. DIVA (Differentiation of Infected from Vaccinated Animals) vaccines can address this issue by using a selected suite of viral antigens, enabling diagnostic tests to distinguish between vaccinated and infected horses.
A) no
C) no. The text does not claim that LAV vaccines are ineffective, but rather that they complicate monitoring the disease. DIVA vaccines, while promising, are not discussed as offering superior protection in efficacy terms.
D) no. LAV vaccines are currently being used in Thailand to control the outbreak, but DIVA vaccines are still in development.
African horse sickness in Thailand: Challenges of controlling an outbreak by vaccination, 2020, EVJ
Which disinfectant showed the best results in terms of cleaning time, culture outcomes, and qPCR results after disinfection of endoscopes contaminated with Streptococcus equi?
A) Ortho-phthalaldehyde (OPA), requiring 12 minutes of cleaning, with no positive culture results but a 73% qPCR-positive rate
B) Accelerated Hydrogen Peroxide (AHP), requiring 8 minutes of cleaning, with no positive culture results and a 33% qPCR-positive rate
C) Water (control), requiring 12 minutes of cleaning, with no positive culture results but a 71% qPCR-positive rate
D) Both OPA and AHP, showing the same efficacy in terms of culture and qPCR results
ANSWER B)
AHP was significantly more effective than OPA in reducing qPCR-positive results, despite both disinfectants eliminating live bacteria as indicated by culture tests.
Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants 2023
When evaluating disinfection methods to remove Streptococcus equi from endoscopes and twitches in an equine clinic, which of the following statements is TRUE according to this study?
A. All tested disinfection protocols eliminated both viable bacteria and DNA of S. equi from endoscopes and twitches.
B. Disinfection with sodium hypochlorite was the only method to remove S. equi DNA from twitches, though this disinfectant poses ecological risks.
C. Complete elimination of S. equi DNA on endoscopes was only achieved using an Automated Endoscope Reprocessor (AER).
D. Field disinfection protocols for endoscopes were insufficient for removing viable bacteria in all cases.
Correct Answer: B. Disinfection with sodium hypochlorite was the only method to remove S. equi DNA from twitches, though this disinfectant poses ecological risks.
Justification:
Option A is false: None of the protocols completely removed S. equi DNA from all samples.
Option B is correct: Sodium hypochlorite was the only disinfectant that eliminated bacterial DNA from twitches, though it is toxic to aquatic organisms.
Option C is incorrect: Although AER showed effectiveness (Results: No viable S. equi was found in bacterial cultures (0 out of 6 samples), and only 1 out of 6 samples remained PCR-positive, showing the highest efficacy in DNA removal among all methods tested), it did not completely remove all bacterial DNA from samples.
Option D is incorrect: Field-disinfected endoscopes showed no viable bacteria post-cleaning, though one sample remained culture-positive (ethanol)
2020 Age-related differences in blood pressure, ultrasound-derived arterial diameters and arterial wall stiffness parameters in horses
Cl= DNA remains detectable, which could cause false positives in PCR.
In the context of screening for Streptococcus equi guttural pouch carriers in horses, which of the following statements is TRUE based on the study findings?
A. Serological testing for antigens A and C is highly sensitive for detecting guttural pouch carriers.
B. A positive serological result for antigens A and C reliably indicates guttural pouch carriage of S. equi.
C. Microbiological sampling is more reliable than serology in identifying S. equi carriers.
D. Horses testing seronegative for antigens A and C are unlikely to be carriers of S. equi.
Correct Answer: C. Microbiological sampling is more reliable than serology in identifying S. equi carriers.
Option A is incorrect: The study demonstrated that serological testing has low sensitivity, missing many guttural pouch carriers.
Option B is incorrect: A positive serology result does not reliably indicate carrier status due to low positive predictive value.
Option C is correct: Microbiological sampling (PCR and culture) directly detects S. equi, making it more reliable than serology.
Option D is incorrect: Seronegative results do not exclude carrier status, as many carriers were seronegative in this study.
2020 Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers
Which of the following statements is TRUE regarding the use of the dual antigen iELISA test in horses vaccinated with the Pinnacle IN vaccine?
A. The iELISA test can reliably distinguish between vaccinated horses and those naturally exposed to S. equi.
B. Horses vaccinated with Pinnacle IN are unlikely to show seroconversion to Antigens A and C in the iELISA test.
C. Pinnacle IN vaccination causes high seroconversion rates to Antigens A and C, affecting the iELISA test’s ability to indicate infection.
D. Only horses with natural S. equi infection show seroconversion in the dual antigen iELISA test.
Correct Answer: C. Pinnacle IN vaccination causes high seroconversion rates to Antigens A and C, affecting the iELISA test’s ability to indicate infection.
Option A is incorrect: The study indicates that the iELISA test does not reliably distinguish between antibodies from vaccination and those from natural infection.
Option B is incorrect: The majority of vaccinated horses in the study seroconverted to Antigen C and a significant portion to both antigens.
Option C is correct: The study found that Pinnacle IN vaccination leads to high seroconversion rates to both Antigens A and C, impacting the iELISA test’s diagnostic accuracy in vaccinated horses.
Option D is incorrect: Vaccinated horses, not only those with natural infection, can show seroconversion in the dual antigen iELISA.
2021 Horses vaccinated with live attenuated intranasal strangles vaccine seroconvert to SEQ2190 and SeM
