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Effectively treating
cats with FHM
Feline hemotrophic mycoplasmosis is a challenge to manage,but the right drugs and careful monitoring help cats recover.
As evidenced by its recent formerly known as feline infectious anemia.
name change, Mycoplas- Without treatment, it is estimated that one- ma haemofelis, formerly third of cats with acute hemobartonellosis known as Haemobarto- ultimately die from severe anemia.1 nella felis, causes a disease Those cats that do recover without ther- in cats that is difficult to apy often suffer from recurrent episodes and diagnose and a challenge to treat. Both the can remain chronically infected for months By Kris Ann Fazio, previous and new terminology are used in or even years, if not indefinitely.2 While this article to explore the current treatments some of these untreated cats may appear for the disease entity seen in feline patients.
clinically normal, they may also have a mild The article discusses the two main drug regenerative anemia for life. Thus, the classes used in treating cases importance of treating hemobartonellosis of hemobartonellosis— extends beyond the immediate clinical pic- antibiotics and corti- ture and becomes important for patients' long-term health and quality of life.
Tetracycline antibiotics are the drugs of the disease.
choice for treating hemobartonellosis.
Doxycycline administered orally at a dose range of 2.5 to 5 mg/kg twice daily for three Timely diagnosis, weeks is the preferred drug for several rea- appropriate therapy sons.1,3,4 First, it is available in an oral sus- and good supportive care are essential pension that is preferable to tablets because in ensuring a positive outcome in tablets can lodge in a cat's esophagus, caus- our patients with feline hemo- ing irritation and scarring that can result trophic mycoplasmosis (FHM), in esophageal stricture.3 Furthermore, doxycycline only needs to be given twice Illustration by Christian Hammer 36 Banfield
a day, whereas other tetracyclines must be corticoid, such as prednisone, helps sup- given three times a day. Finally, doxycycline press the immune response and slow the tends to cause fewer gastrointestinal side removal of the patient's RBCs.1,4 (Admin- effects than other tetracyclines. To further ister prednisone at 1 to 2 mg/kg orally twice decrease the likelihood of gastrointestinal a day; decrease the dosage gradually as the side effects, give doxycycline with food.3 packed cell volume [PCV] increases.) Fre- During oral antibiotic treatment, monitor quently, steroids may be used because the Pets for fever, anorexia, vomiting and, immune response is such a large part of the although rare, liver toxicosis. disease. However, concurrent disease may If doxycycline is not available or if the cat preclude the use of steroids.
cannot tolerate it because of side effects, use Remember to teach the Pet owner that a fluoroquinolone antibiotic (e.g., enro- while most steroids are well-tolerated by floxacin at a dose range of 2.5 to 5 mg/kg cats, they do cause immunosuppression and orally per day for three weeks). The full dose should be avoided in M. haemofelis-infect- can be given at one time, or it can be divid- ed cats with heart disease, diabetes mellitus ed into two doses per day. Caution is advised or concurrent infections.3 when using enrofloxacin in cats; do not exceed a total dose of 5 mg/kg daily because of the risk of ocular toxicosis, a rare idiosyn- Because of the nature of an M. haemofelis cratic reaction characterized by mydriasis, infection, patients can experience a gradual retinal degeneration and blindness.
or precipitous drop in hematocrit (some patients may experience both as the disease progresses), resulting in mild to life-threat- Killing the infectious agent is only half the ening anemia. If a severe, rapid hemolytic battle in treating cats with FHM. A large crisis occurs (e.g., PCV declines to less than part of the clinical syndrome is due to the 15 percent), a blood transfusion may be nec- immune-mediated destruction of infected essary. When considering a transfusion in a red blood cells (RBCs) by erythrophagocy- feline patient, remember that crossmatching tosis.2,4,5 Therefore, treatment with a gluco- should always be performed because anti- Are Dogs at Risk?
Unlike cats, dogs rarely contract hemobartonellosis. The organism that caus-
es disease in dogs, Mycoplasma haemocanis (formerly known as Haemo- bartonella canis), is not generally considered a problem except in dogs that have been splenectomized or have concurrent illness and splenic dysfunc- tion, so consequently cannot filter infected red blood cells.1 When feline patients share a home with a dog, educate the client that the disease affect- ing their cat cannot be transmitted to their dog. Explain that the two organ- isms, Mycoplasma haemofelis that affects cats and M. haemocanis that affects dogs, are distinct and do not cause infection in the other species.
1. Giger U. Hemobartonellosis. In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine.
5th ed. Philadelphia, Pa: WB Saunders Co, 2000:1799-1800.
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bodies to foreign blood group antigens nat- should begin with rehydration if it is indicat- urally occur in the feline species (see Feline ed, as well as antibiotics and steroids where Blood Crossmatching, page 40). If the criti- appropriate, and then the doctor should cal nature of the case precludes time for evaluate whether the patient needs a blood crossmatching, give blood based on blood transfusion. Be sure to monitor for cardiac type, which can be determined using com- arrhythmias, syncope and dyspnea that can mercial kits. If a blood transfusion becomes sometimes be seen as a result of the anemia.
a necessary part of the treatment plan, use Once initial therapy has been started, if the the following volume guideline for feline patient continues in a critical state, consider patients: Administer a total volume of 4 to referral to a facility that provides 24-hour 5 mL/lb (8 to 12 mL/kg)6 at a rate of 1 monitoring during hospitalization. ■ 6-lb cat: 30 mL given over 30 min The response to treatment of mycoplasmo- ■ 10-lb cat: 40 mL given over 40 min sis is largely how we monitor and predict the prognosis of our patients. Another indi- cator of improvement is appropriate an Hemobartonellosis is an opportunistic infec- increase in PCV, which should be evaluat- tion; therefore, diagnosis and management ed after about one week of therapy.1 Also, of concurrent disease is critical to a positive it is important to keep in mind that none of outcome. Viral infections, abscesses, other systemic illnesses, trauma, stress and surgery are complicating factors. A significant num- ber of cats with FHM are also feline leukemia virus (FeLV) positive, and it has been shown that concurrent infection with M. haemofelis and FeLV exacerbates the anemia.1,7 Interestingly, simultaneous infec- tion with feline immunodeficiency virus does not appear to worsen the anemia.4 When the patient is extremely debilitated and especially when other infections or dis- ease processes are present, intravenous fluid administration can be life-saving. Con- sideration should also be given to adminis- tering glucose-rich fluids, particularly if the patient has been anorexic, is otherwise very ill or if the Pet is very young or underweight.
Even with a low PCV, it is important to expand the circulating volume with crystal- loid fluids so that vital organs receive an increased amount of the existing hemoglo- bin. Initial therapy for patients with FHM July/August 2006 39
Feline Blood Crossmatching
Cats have three basic blood types denoted with an AB system. An individual cat may
have blood type A, B or, very rarely, AB (Table 1). All cats except those with type AB blood have naturally occurring alloantibodies directed against the other blood type. Type B cats have high levels of these alloantibodies, which can cause strong agglutination and hemolysis of type A blood if these cats are transfused with it. Because of this, type B cats are in danger of an immediate transfusion reaction following the first transfusion of incompatible type A blood.
Type A cats have lower levels of alloantibodies to type B blood, which causes milder agglutination and hemolysis. So there are only minor transfusion reactions if type A cats receive type B blood; however, the survival time of these transfused cells is decreased.
Type AB cats can be safely transfused with type A or type B blood.
Neonatal isoerythrolysis can occur if type A or type AB kittens are born to type B queens. This occurs when newborn kittens nurse and ingest antibodies from the queen.
This can be a cause of fading kitten syndrome.1 1. Bracker KE, Drellich S. Transfusion Reactions. Compendium 2005;27:500-512.
Table 1: Frequency of Occurrence for Feline Blood Types
Percent of Cats with Blood Type
Northeastern United States Southeastern United States Southwestern United States West Coast United States United States (total) Australia (Brisbane) Table 2: Feline Breeds with Type B Blood
Percent of Breed with Type B Blood*
American Shorthair, Burmese, Ocicat, Oriental Shorthair Maine Coon, Norwegian Forest Abyssinian, Japanese Bobtail, Persian, Himalayan, Somali, Sphinx Cornish Rex, Exotic Shorthair British Shorthair, Devon Rex *Type A percentages can be calculated by subtracting type B percentages from 100 percent.
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the tetracyclines can clear the infection blood donors for hemobartonellosis completely, so you may detect the organ- because, as we know, once infected with M. ism on a blood smear in the face of an haemofelis, a cat may always be a carrier.
increasing PCV and improvement in the Hemobartonellosis may be difficult to patient's condition. Remember that with- diagnose, but once a diagnosis is made, out treatment, approximately one-third of treatment of uncomplicated cases usually cats with acute hemobartonellosis will die.1 results in a positive outcome. Careful If a timely diagnosis is made, cats generally patient monitoring, appropriate drug ther- respond well and quickly to treatment, and apy and vigilant supportive care are all the prognosis for uncomplicated hemobar- integral to successfully completing the tonellosis is good.5 However, it is impor- FHM treatment puzzle. Client education is tant to note that many cats remain carriers paramount in preventing the disease, but it for the rest of their lives because the organ- is also important in preventing the spread ism may not be completely eliminated from of the organism once discovered. All these the blood even with treatment.2,5 The good factors allow us to maximize both the news is that these cats seldom become clin- length and quality of life for our feline ically ill once their PCVs have normalized patients, thereby making life better for Pets and they have recovered.1 and their families. References
1. Harvey J. Hemobartonellosis. In: Tilley LP, Smith FWK Jr,
While there is no vaccine to prevent infec- eds. The 5-Minute Veterinary Consult: Canine and Feline.
tion with M. haemofelis, there are some Baltimore, Md: Williams and Wilkins, 1997:648.
steps that can decrease the risk of exposure.
2. Breitschwerdt E. Hemobartonellosis. In: Ettinger SJ, It has been shown that risk factors for FHM Feldman EC, eds. Textbook of Veterinary Internal Medicine.
5th ed. Philadelphia, Pa: WB Saunders Co, 2000:406-407.
include positive status for FeLV, lack of vac- 3. Plumb DC. Veterinary Drug Handbook. 4th ed. Ames, cinations, history of cat-bite abscesses, age Iowa: Blackwell Publishing Co, 2002:300-303, 309-312, less than 4 years and an outdoor roaming 684-692, 779-783.
4. Giger U. Hemobartonellosis. In: Ettinger SJ, Feldman status. 2,5 Hence, a thorough preventive-care EC, eds. Textbook of Veterinary Internal Medicine. 5th ed.
schedule that includes testing for FeLV, Philadelphia, Pa: WB Saunders Co, 2000:1799-1800. appropriate vaccinations, neutering (thus 5. Carney HC, England JJ. Feline hemobartonellosis. Vet reducing the propensity for fighting, which Clin North Am Small Anim Pract 1993;23:79-90. 6. Phillips JD. Banfield Blue Book. Portland, Ore: Banfield, can result in cat bites) and keeping cats The Pet Hospital, 2003:15-16.
indoors could significantly reduce the risk of 7. Messick JB. Hemotrophic mycoplasmas (hemoplasmas): a feline Pet contracting hemobartonellosis.
a review and new insights into pathogenic potential. Vet A good flea-control program with either Clin Pathol 2004;33:2-10.
8. Bracker KE, Drellich S. Transfusion Reactions.
Advantage™ (Bayer) or Frontline™ (Merial) can help protect cats from fleas that may carry the M. haemofelis organism.5 Kris Ann Fazio, MS, DVM, a 2003 graduate
of the University of Tennessee College of Client education is the key to gaining Veterinary Medicine, joined Banfield in Dothan, compliance with these basic steps that can Ala., in 2003 and is now chief of staff in help safeguard feline patients. Clinicians Hillsboro, Ore. She shares her home with should also thoroughly screen all potential a guinea pig named Snow.
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