Haemobartonella, Haemobart.,
feline infectious anemia.
Essentially
all cats have the potential to be infected with Haemobartonella
felis.Cats infected
with feline leukemia virus appear to be at higher risk for
infection and are likely to have more severe signs of illness.
Haemobartonellosis, or feline infectious
anemia, is a parasitic disease caused by Haemobartonella
felis. The disease process begins when H. felis organisms
attach themselves to the red blood cells of infected
cats. H. felis may be spread by a number of routes,
although fleabites are thought to be the major mode of
transmission. While some infected cats have no symptoms,
others may develop severe anemia and illness. The infection
is diagnosed microscopically when the organisms are found
on the surface of red blood cells in a blood smear. However,
since the organisms may not always be present, treatment
is often initiated in an anemic cat if there is no other
explanation for the anemia. Specific treatment for feline
infectious anemia includes tetracycline antibiotics and
prednisone. Patients may require supportive care, including
blood transfusion. Although treatment does not eliminate
the infection completely, cats that survive are thought
to have a good long-term outlook.
The severity of clinical signs associated
with Haemobartonella infection usually corresponds
to the degree of anemia present, or the speed with which
it develops. Cats with mild anemia may show no overt signs
of illness. In severely anemic cats, or in cats that rapidly
become anemic, signs can include depression, lethargy, inappetance,
pallor, jaundice and splenomegaly. The temperature may be
elevated, but in cats with life-threatening anemia, the body
temperature is often subnormal.
Cats with mild, Haemobartonella-induced
anemia may not show any symptoms of disease. In cats with
severe anemia, or in cases where the anemia develops quickly,
symptoms include weakness, depression, reduced appetite,
decreased activity, and pale or jaundiced mucous membranes.
Cats that are severely ill may be in shock, with below normal
body temperature.
Feline infectious anemia is caused by
the organism Haemobartonella felis. This organism
may be spread by fleabites, cat bites, blood transfusion,
and by mothers to their kittens. Some cats infected with Haemobartonella have
no symptoms, while others can develop life-threatening anemia.
Cats that are also infected with feline leukemia virus are
expected to have more severe signs of illness. Symptoms can
include fever, depression, and loss of appetite. Signs of
anemia may include lethargy, weakness, pale or jaundiced
mucous membranes, and increased respiratory rate and effort.
Severely affected cats may appear to be prostrate and depressed,
or in shock. They can die suddenly with no apparent warning.
The
anemia arises as infected red blood cells are attacked
and destroyed by the immune system. The spleen is one of
the major sites of red blood cell destruction. If the hemolytic
process is severe, pigments from red blood cell breakdown
may accumulate in the blood stream, resulting in jaundice.
Haemobartonella should be considered as a possibility
in any anemic cat or any cat with evidence of hemolysis.
The diagnosis is based on microscopic identification
of H. felis on a blood smear. Since the appearance
of H. felis on red blood cells is cyclical,
the organisms may not be present all the time. In many
cases, treatment is begun even if the diagnosis is
only suspected and not confirmed.
Treatment of haemobartonellosis includes tetracycline
antibiotics and prednisone. Blood transfusions may be
required in patients with severe anemia. In cats that
recover, a chronic carrier state develops. These chronic
infections may persist for the life of the cat. Without
treatment, as many as one out of every three cats with
haemobartonellosis will die from the disease. Although
they may be carriers of the organism, successfully treated
cats have a good long-term outlook. Control of flea and
tick infestations may help prevent re-infection with Haemobartonella.
The confirmation of H. felis infection
rests on the microscopic identification of the organisms
on the surface of red blood cells on a blood smear. It is
easy to confuse the organisms with other red blood cell changes.
The presence of the organisms in an otherwise normal cat
may be an incidental finding. The absence of the organism
in an anemic cat does not rule out the disease, since their
appearance in circulation appears to be cyclical. Furthermore,
the parasites clear rapidly upon treatment with antibiotics,
making detection difficult. Special laboratory stains may
be helpful in identifying the organism microscopically. A
sophisticated test called polymerase chain reaction, or PCR,
may also help establish the diagnosis. This test looks for
genetic material unique to H. felis.
With successful treatment, the outcome
for cats with feline infectious anemia appears to be
good. Successful treatment does not completely eliminate
the organism, and previously affected cats may serve
as carriers. Some authorities have suggested that carrier
cats can relapse if their body defenses are weakened.
However, no clinical evidence exists to support this
concept.
The cause of Haemobartonellosis is an
organism called Haemobartonella felis, a parasite
that attaches to the surface of red blood cells in infected
cats. Fleabites may be the primary means of spread. The organism
can be passed from mother cats to their kittens, but it is
not known whether this spread occurs prior to birth, during
birth, or through nursing. The organisms may be passed via
blood transfusion. Some authors suggest that cat bites may
also transmit the organisms.
Treatment for haemobartonellosis includes
blood transfusion, antibiotics, and prednisone. Blood
transfusions are used to temporarily stabilize severely
anemic cats, replenishing the number of red blood cells.
The need for transfusion is based on the cat's overall
condition.
Tetracycline antibiotics are employed to eradicate as many
H.
felis organisms as possible. Doxycycline is probably
the most frequently prescribed antibiotic in this class because
it usually causes fewer side effects than other tetracyclines.
Suppression of appetite, nausea or vomiting are common signs
of adverse drug reaction. The drugs do not completely eliminate
the infection, but they appear to lessen the severity of
the disease.
Prednisone is frequently prescribed in cases of feline infectious
anemia. This corticosteroid medication is used to help block
immune system-mediated red blood cell destruction.
Haemobartonellosis remains one of the few specifically treatable
causes of severe anemia in cats. In many circumstances, treatment
is started when the disease is suspected, even if the organisms
are not identified.
Careful attention to elimination of
fleas and the prevention of flea infestation should reduce
the possibility of flea-borne spread of H.felis.
Screening of donor cats to be sure they do not harbor
the Haemobartonella organism may prevent spread
via blood transfusion.
