ACVIM Required Reading - Haemolymphatic Dz

Question 1

What plant, in addition to red and silver maples and wild onions, has been reported to cause Heinz body anaemia and methaemoglobinaemia in horses? What is the toxic agent in this plant and what body fluid can it be detected in?

Answer 1

• Pistachio trees (Pistacia spp)
• Pyrogallol or gallic or tannic acids (converted to pyrogallols in the equine GIT).
• Urine pyrogallol concentration.

Ref: J. Vet. Intern. Med. 2015;29:410–413.

Question 2

Do concurrent hyperglycaemia and endotoxaemia result in more severe coagulation abnormalities in horses than endotoxaemia alone?

Answer 2

• 6 horses LPS-saline infusion vs 6 horses glucose-LPS infusion; measured PT, APTT, TAT and thromboelastometry (clot characteristics).
• Minor alterations in coagulation parameters identified for each group were most likely not clinically relevant.
• Observed differences between groups do not suggest that concurrent hyperglycemia and endotoxemia are associated with greater coagulation abnormalities in horses.

Ref: J. Vet. Intern. Med. 2013;27:347–353.

Question 3

Is Bartonella present in horses in North Carolina? What is the best method for testing?

Answer 3

• 47 healthy horses, 15 sick foals, 22 horses with musculoskeletal manifestations, and 8 horses w colic were tested for Bartonella.
• Methods: IFA serology and PCR before and after BAPGM (Bartonella alpha-Proteobacteria Growth Medium) enrichment blood culture.
• Results: 0 positive IFA; 3 Bartonella species, B. henselae, B. vinsonii subsp. berkhoffii (genotypes I and III), and a Bartonella species with closest homology to Candidatus Bartonella volans, were PCR-amplified and sequenced from blood or BAPGM enrichment blood culture samples from 1/47 healthy horses, 3/15 sick foals, 5/22 horses with musculoskeletal disease, and 0/8 horses with colic.
• Based upon the IFA assays used in this study, serology was not useful in establishing prior exposure to or infection with a Bartonella sp.

Ref: J. Vet. Intern. Med. 2012;26:1408–1412.

Question 4

List blood and clinical examination changes that occur in horses after experimental infection with Bartonella.

Answer 4

• 3/4 B. henselae-inoculated horses seroconverted, whereas only 1/4 B. bovis-inoculated horse was weakly seropositive.
• B. henselae was amplified and sequenced from BAPGM blood culture as well as a subculture isolate from 1 horse, blood from a 2nd horse, and BAPGM blood culture from a 3rd horse although a subculture isolate was not obtained.
• CSx: mild to moderate limb oedema, mild cervical LN enlargement, 1 horse mild medical colic; no fever.
• Detection of Bartonella sp. in blood after experimental inoculation supports bacteremia and seroconversion.
• Culture with BAPGM may be required to detect Bartonella sp.
• Although mild clinical signs followed acute infection, no long-term effects were noted for 2 years post-inoculation.

Ref: J. Vet. Intern. Med. 2012;26:377–383.

Question 5

Does storage of equine blood affect the result of cross-matching testing?

Answer 5

• Blood samples collected and cross-matching performed on fresh blood and blood stored for 1-4wks.
• Cross-match was repeated on 6 fresh samples from each horse to testing repeatability.
• Equine blood crossmatching is repeatable using fresh blood.
• Decreased apparent compatibility after storage makes exclusion of compatible donors more likely than mistaken administration of incompatible blood.
• These data suggest that fresh samples should be collected from potential donors before crossmatching equine blood.

Ref: J. Vet. Intern. Med. 2012;26:662–667.