1. Michael Foust, Cristina Mendoza, and Lizeth Cueto
Pigeon Fever (Pigeon Breast, Dryland Distemper, and Colorado Strangles)
Michael Foust, Cristina Mendoza, and Lizeth Cueto

2. Why is it important? Remerging Equine disease!
Also affects sheep (more of a problem in Europe), goats, and cattle
Worse in drought conditions, currently in areas like California and Texas
Humans can possible get infected by exposure!

3. What is Pigeon Fever?
Bacterial infection caused by Corynebacterium pseudotuberculosis
Two strains
Nitrate Negative (sheep and goats)
Nitrate Positive (horses)
Nitrate Positive and Negative (cattle)
There are three equine forms of the disease, ulcerative lympthangitis (lympth infection), external abscesses, and internal infection.
Transmission is via biting insects (most commonly flies), animal to animal, object to animal, dirt to animal.
Currently disease is not zoonotic, but has a potential to be.
Pigeon fever has no direct relation to pigeons.
Symptoms result in swelling of the chest which resembles the puffed out chest of a pigeon.

4. Corynebacterium pseudotuberculosis
A gram positive, rod shaped, non-spore forming capsulated bacteria with worldwide distribution
Two different strains
Nitrate positive (sheep/goats)
Nitrate negative (horses/cattle)
Produces a variety of exotoxins, including phospholipase D and sphingomyelinase. The toxins degrade the endothelial cell wall, increase vascular permeability, which results in edema and external abscesses. o

5. Bacteria Microbiology Cont….
Bacterial Culture from external abscess.
Blood agar and then cultivated for 72 hours.
Reverse CAMP test used in positive identification of Corynebacterium pseudotuberculosis infection.
Internal abscess; perform a Synergistic Hemolysis Inhibition (SHI) test

6. Corynebacterium pseudotuberculosis on blood agar
Corynebacterium pseudotuberculosis on blood agar. Cultivation within 72 hours, in an aerobic atmosphere enriched with 5% carbon dioxide. Identified with API Coryne (bioMérieux, France). Identification then confirmed by 16S rRNA gene sequencing.

7. Explains the presence of pain and edema at the site of infection
Corynebacterium pseudotuberculosis
Phospholipase D in corynebacterium pseudotuberculosis is similar to the phospholipase D of the Brown Recluse spider (Loxosceles reclusa)!!!
Explains the presence of pain and edema at the site of infection

8. Mechanism of Transmission
Insects such as the horn fly, house fly, and stable fly act as mechanical vectors for transmission of this disease to horses.” Dr. Spier, AAEP They land on infected soil, infected abscesses, objects that pus from infected abscess dripped on (stall, ground, bedding) and bacteria is now all over their legs/wings/body. Next, they carry bacteria to the horse and it is seeded onto pre-existing horse wounds, cuts, abrasions, surgical sites, and bacteria then multiplies and creates huge abscess issues.

9. Mechanism of Transmission
Horse to another Horse– pus out of abscess of infected Equine Pigeon Fever/Horse Pigeon Fever horse smeared onto another horse’s wounds/cuts/abrasions and bacteria multiply.
Horse to object to another horse – Pus out of abscess lands on bedding, soil, fence posts….etc, and another horse wanders by and smears it into pre-existing wound/cut/abrasion.

10. Mechanism of Transmission
Dirt to horse – roll in contaminated soil and bacteria gets into pre-existing wounds.

11. Mechanism of Transmission
Same mechanisms for sheep, goats, and cattle; rolling in contaminated soil, animal to animal, licking abscesses, etc.

12. Corynebacterium pseudotuberculosis Infection (Pigeon Fever in horses)
Three Forms:
1. External Abscesses
About 91% of cases present with abscesses in the lymph nodes of the pectoral and chest region
2. Internal Abscesses
8% of cases present no history of previous external abscesses, 63% of cases show history of external abscesses or history of living in areas where other horses had been diagnosed with external abscesses
3. Ulcerative lymphangitis (lymph infection)
Least common in the U.S. with 1% of cases, but the most common worldwide

13. External Abscesses
May occur anywhere on the body but are most common in the pectoral region (breast muscles) or ventral abdomen (along the midline of the belly)
Infection of the lymph nodes deep in the pectoral muscles or at the thoracic inlet leads to swelling of the soft tissues in the proximal forelimb and pectoral region
Initial symptoms can go undetected and the ruptured abscess is the first sign observed

14. Diagnosis for External Abscesses
Signs of systemic illness are usually not present, however about 25% of cases develop fever (104℉).
Diagnosis is based upon the inflammation of soft tissue and edema surrounding the lymph node area, as well as identification of abscesses that are filled with tan odorless discharge.
Confirmation of nitrate positive Corynebacterium pseudotuberculosis through the use of culture examination.
Hair loss and rupture of the skin, that result in drainage
lethargy and lameness.

15. Treatment for External Abscesses
Lancing and drainage with iodine solution or saline water is often the only treatment required for external abscesses.
Daily flushing of the wound with saline or water for a period of 3-5 days will often result in resolution of the infection.
Usually occur to deep muscles (pectoral and triceps) and use of ultrasound to guide lancing is beneficial.
If systemic illness is present then diagnostic testing for internal abscesses should be conducted, and put on antimicrobial if present
Trimethoprim-sulfa (5 mg/kg based on the trimethoprim fraction, twice daily orally) or procaine penicillin (20,000 U/kg twice daily intramuscularly)
Controversial Treatment.
Inject abscess with 10% formalin solution that kill bacteria in lymph node
Infects entire animal and is extremely painful
Causes abscesses to dry up and slough off

16. Our Concerns with the Formalin Injection
External abscesses are the most common type of Pigeon Fever seen in horses. Although the abscesses look extremely painful, quality of life of the horses is not usually compromised.
Rupture and draining of the abscesses usually occur on their own, but veterinarian intervention is recommended.
Where does that intervention cross the line?
Veterinarian’s oath for “the prevention and relief of animal suffering.”
Using 10% formalin injection is extremely painful because it affects the entire animal.
The use of this injection does induce faster sloughing than the draining method, but is it worth putting the animal in more pain?
The patient should be made as comfortable as possible
Adequate time and patience should be taken to properly treat the patient

17. Internal Abscesses
Attacks internal organs, with abscesses appearing in lungs, liver, spleen or kidney
Internal infection cases are associated with high fatality rates because diagnosis can be challenging

18. Diagnosis for Internal Abscesses
Diagnosis is very challenging:
Use of synergistic hemolysis inhibition test with serology titers
Measures antibodies to an exotoxin of Corynebacterium pseudotuberculosis
Titers greater than 1:512 together with the presence of leukocytes and hyperfibrinogenemia points to internal abscesses
Concurrent external abscesses
Biochemical profiling with elevated hepatic enzymes usually present
Examining affected tissue
through the use of ultrasounds or radiographs
Decreased appetite and lethargy
Signs of respiratory disease
Abdominal pain

19. Treatment of Internal Abscesses
Expensive and requires long term treatment and commitment on the part of the owners
Site of infection and penetration are used as microbial guidelines for administration of antimicrobial therapy.
A combination of rifampin (2.5-5 mg/kg twice daily) with broad spectrum antimicrobials like ceftiofur (2.5-5 mg/kg twice daily intramuscularly or intravenously) has been highly effective
Enrofloxacin (7.5 mg/kg once dailly orally) has also been effective
Penicillin is used under special circumstances but only delays infection maturation process

20. Ulcerative lymphangitis
Usually associated with concurrent external abscess
Infection of limbs with swelling and multiple draining lesions usually on the hind legs.
This is the less common form in North America
This form of Pigeon Fever is very painful and can be fatal

21. Diagnosis for Ulcerative lymphangitis
Concurrent with external abscesses
Signs of Systemic Illness
Lethargy
Fever
Severe lameness
Anorexia
Most common in hind limbs
Biopsy of skin and subcutaneous tissue

22. Treatment for Ulcerative lymphangitis
Aggressive and early treatment is required:
Horses need to be put on high levels of NSAID (anti-inflammatory), to manage pain and swelling.
Administration of intravenous antimicrobials (ceftiofur or penicillin G) in combination with rifampin (antibiotic) to prevent lameness and limb swelling
Oral antimicrobials (trimethoprim sulfamethoxazole) are used later in combination with rifampin to prevent relapse.
Physical therapy, including hydrotherapy, hand walking, and leg wraps, as well as NSAIDs are recommended.
Daily flushing of the wound with saline or water for a period of 3-5 days will often result in resolution of the infection.

23. Corynebacterium pseudotuberculosis Infection (Pigeon Fever in Cattle)
Ulcerative granulomatous appear in three forms:
Cutaneous
Mastitic
Visceral
A decrease in milk production is common.
Necrosis and ulcerative dermatitis on heels of foot occurs in heifers.
Lameness is also a common sign of pigeon fever in both cattle and horses.

24. Diagnosis and Treatment
Ulcerative granulomatous lesions
Histological and bacteriological examinations
Necrotic-ulcerative dermatitis on the heel of hoof
Treatment:
Isolation of affected animals
Local treatment of antiseptics
Similar treatment as seen in horses

25. Caseous Lymphadenitis (CL) (Pigeon Fever in Goats)
Also results in abscesses as a result of swelling, ruptures, and drainage of pus from lymph nodes.
Decreased milk production is a common result as well as decrease in body weight and reproductive efficiency.
Clinical Signs
Enlarged lymph nodes with thick walls and filled with a green colored pus. The most commonly affected lymph nodes are the mandibular, prescapular, prefemoral, and supramammary.
Internal lymph nodes of the chest and abdomen are not as common
Vaccination is available for management of disease

26. Caseous Lymphadenitis (CL) (Pigeon Fever in sheep)
Sheep usually get infected when they are housed in tight quarters or gathered in herds.
Occurs mostly in Europe
In some cases internal abscesses occur when the liquid from the abscesses are ingested

27. Diagnosis of Caseous Lymphadenitis (CL)
Swelling of subcutaneous lymph node areas
Heard history of Caseous Lymphadenitis.
Aspiration and collection of abscess for diagnostic testing and identification of culture.
Serologic tests such as the synergistic hemolysis inhibition test.

28. Humans/Zoonosis??? Some possibility of a zoonosis but local
Very few documented cases worldwide in human population, rare to have it mutate into a strain that will infect humans rapidly
Usually from handling of animals from animal caretakers or Veterinarians

29. Demographics
Equine Pigeon Fever/Horse Pigeon Fever is a worldwide infectious disease. In the US, was mostly in West Coast however, has moved south (Florida, Alabama, Texas, Louisiana), all southwestern states (Arizona, New Mexico, Idaho), mid-west (confirmed cases in Oklahoma, Kansas, Colorado, Missouri) also Connecticut and Kentucky
Why?

30. Demographics Cont….
Ease of trailering makes Equine Pigeon Fever/Horse Pigeon Fever a problem all over the USA. Due to the fact that bacteria grow in the soil, once within soil, there is no way to get rid of it – the soil cannot be treated to lower or eliminate bacteria!
Drought creating a problem as it thrives in drier hotter conditions
Can live in soil up to 8 months or more; can travel long distances in transmission miles

31. Demographics Cont… Several drought areas currently in the US.
Since, drought creates a bigger problem, it thrives in drier hotter conditions!
Affected areas in US increasing in area and intensity due to increasing drought conditions

33. Problems of Infection Spreads easily in animals
No current effective vaccine against infection
No geographic bounds; worldwide disease problem
Very costly to equine/animal owner for treatment over long periods
Can become a local zoonosis or local epidemic

34. Prevention Isolate animal first!
When treated infected animal (flushing, wiping out wounds), it is important to handle 4x4s, gloves, and catheters correctly and throw them away quickly to prevent human transmission
Change out hay, feeding troughs, and bleach areas
Meticulous wound care (topical fly repellants, antimicrobial ointments and bandages) to prevent further infection from contaminated environment
Care should be taken to prevent excessive contamination of the environment during lancing and flushing of the wound.

35. Future Treatment and Prevention
Vaccine Solutions?
No vaccines were available to horses until recently
-Vaccine under conditional license, but recommended because of low adverse reaction rates
-efficacy not yet proven
Some possibility for Sheep/Goats
-Vaccine available, but only recommended if
eradication methods have failed
-Has an efficiency of 70-80% in preventing (CL) manifestations
-Only makes it harder for disease to thrive in animal not eliminate from animal
-Causes severe reactions in infected patients
As future veterinarians, horse administration of this vaccine would not be recommended due to possible adverse reactions and questionable efficacy. However, future advances in research can lead to a more promising and reliable vaccine.

36. Summery
Disease: Pigeon Fever caused by Corynebacterium pseudotuberculosis
What happens: Bacteria releases exotoxins that degrade endothelial cell walls, increase vascular permeability, and result in edema and external/internal abscesses.
Affects: Horses, Cattle, Sheep, and Goats
And Remember!!
Pigeon Fever cases have increased due to recent droughts affecting several states in the U.S. Early detection is crucial for successful diagnosis and treatment of the disease. Future advances in vaccinations for pigeon fever could reduce overall incidence and fatality rates.

37. References Articles
Kilcoyne, I., Spier, S. J., Carter, C. N., Smith, J. L., Swinford, A. K., & Cohen, N. D. (January 01, 2014). Frequency of Corynebacterium pseudotuberculosis infection in horses across the United States during a 10-year period. Journal of the American Veterinary Medical Association, 245, 3,
Szonyi, B., Swinford, A., Clavijo, A., & Ivanek, R. (February 01, 2014). Re-emergence of Pigeon Fever (Corynebacterium pseudotuberculosis) Infection in Texas Horses: Epidemiologic Investigation of Laboratory-Diagnosed Cases. Journal of Equine Veterinary Science, 34, 2,
Barba, M., Stewart, A. J., Passler, T., Wooldridge, A. A., Santen, E., Chamorro, M. F., Cattley, R. C., ... Hu, X. P. (March 01, 2015). Experimental Transmission of Corynebacterium pseudotuberculosis, Biovar equi in Horses by House Flies. Journal of Veterinary Internal Medicine, 29, 2,

38. References Websites