Haemobartonellosis is a mild infection presenting only a slight
febrile reaction but led to more or less pronounced anaemia. Under challenge, a
febrile icterohaemorrhagiae with anaemia and haemoglobinuria can appear. It is
important in the tropics because a superinfection with another vector borne
disease can be complicated by haemobartonellosis.
ETIOLOGY
Gram positive non acid fast apicellular ricketsial parasite
of erythrocyte belonging to the genus- Haemobartonella and family-
Anaplasmataceae. It occurs in the red blood cells and cells of the lymphatic
system, spleen, liver and kidneys. The
host range of H.felis and H.canis appears to be restricted to cats and dogs.
Although experimental subclinical infection of cats with H.canis has been
reported.
PATHOGENESIS
Experimentally, Haemobartonella felis infection can be
transmitted by intraperitoneal or intravenous injection or oral administration
of infected blood. Blood sucking arthropod like fleas, although this means has
not been reported in cats. Female cats can transmit the disease to newborn in
the absence of arthropods. Blood transfusion by carrier cat but in dogs, ticks
especially Rhipicephallus sanguineus is an important reservoir and vector of infection.
Transfusion in dogs is also possible but not as important in cat. Since
recipient dog must have been splenectomised before clinically significant
disease occurs. Oral administration of infected blood has also been reported
but in dog in utero or through nursing has not been successfully carried out.
In the cat, the severity of the disease due to Haemobartonella felis varies from
mild anaemia without clinical signs to cats markedly depressed and die due to
severe anaemia. This disease can be divided into four phases namely;
preparasitemic, acute, recovery and carrier cases. Preparasitemic phase lasts for
about 1-3 weeks after intravenous injection and 22-51 days after splenectomised
cats have been given infected blood orally. Acute phase represents the time from
the first to the last major parasitemia. This phase often last for more than
two months as the case persists.
Occasionally, cats die quickly following the occurrence of massive parasitemia and
reduction in packed cell volume early in disease course. Parasites appear in
blood in cyclical manner within discreet parasitemic episode or incident. The
number of parasites peaks over 1-7 days followed by a rapid reduction. The
synchronized disappearance of organisms from blood can occur in two hours or
less. Few if any parasites are seen in blood films or several days following
parasitemic episodes. There is a rapid decrease followed by rapid increase in
packed cell volume occuring in association with the appearance or disappearance
of the organism from the blood. The fluctuations or variations in packed cell
volume appear to be associated with splenic seizing of parasitized red blood
cells and later release of non-parasitised red blood cells. In other instances,
packed cell volume remains decreased or continues to decrease for one or more
days after a parasitemic episode probably due to red blood cell destruction.
The repeatitive parasitemic occurence appears to damage red blood cell and
shorten its life span. Some damages of red blood cell may be caused by
parasites but immune mediated injury appears to be more important. The cat that
survives the uncomplicated acute phase or stage without therapy enters recovery
phase. Organisms are commonly observed in low numbers in the blood but do not
occur as discreet parasitemic episode. Cats that recover from acute infection
remain clinically infected for months, years or even or life. Intact organisms
have been seen within phagocytic
vacuoles or spleen among macrophages, hence some organisms survive within the
cells instead of being eliminated by immune mechanisms and this accounts for
indefinite chronically infected state called carrier phase. Cats appear
clinically normal with or without normal packed cell volume or mild
regenerative anaemia. Low numbers of organisms are regularly observed in some
cats but in others, no organism may be visible in blood film for weeks. Cats
appear to be in balance state in which replication is balanced by phagocytosis
and removal.
IN DOGS,
Unlike in cats, the majority of non-splenectomised dogs infected
with H.canis do not get clinical signs and may not be anaemic or has sufficient
number of organisms present in blood to be identified on routine blood film
examination. The prepatent period following intravenous injection of
splenectomised dog vary from 1-2 days to over 2 weeks. Some have been
characterized by rapid developing anaemia with nearly constant parasitemia.
Death occurs within one month following inoculation. In other dogs, anaemia
development is more gradual occuring as repeatitive parasitemic episodes. Apart
from splenectomy being necessary for this disease to occur in dogs, unsplenectomised
dogs with concurrent erlichiosis, babesiosis, bacterial or viral diseases,
immunosuppressive drugs, and dogs with abnormal spleen have come down with
haemobartonellosis.
CLINICAL FINDINGS IN CATS
Depression, weakness, lack of appetite, weight loss,
paleness of mucous membrane, splenomegaly(abnormal enlargement of the spleen).
Icteric mucous membrane. If anaemia develops gradually, there may be weight
loss and the cat is alert and bright but if packed cell volume drops early in
disease in association with severe parasitemia, little weight loss is obviously
observed with mental depression. Rectal temperature is normal except in acute
disease stage when the rectal temperature may be increased by 50%.
CLINICAL FINDINGS IN
DOGS SPLENECTOMISED
The dog is lethargic with pale mucous membrane as anaemia
develops but have normal rectal temperature and appetite.
DIAGNOSIS
Haemobartonella felis can be demonstrated in red blood cell
employing acridine orange stain or flourescent
antibody staining method for accurate detection of Haemobartonella felis.
Post motem findings of a large spleen, chronic passive congestion of the liver
and hyperplasia of bone marrow. It is recommended that blood smears may be made
and examined sequential for several days before cat is declared free from
Haemobartonella felis because of parasitemic occurence.
PATHOLOGY FINDINGS OR GROSS NECROPSY FINDINGS IN CATS
The gross necropsy findings or lesions in cats are pale
appearing tissues, emaciation, spenomegaly, slight to moderate icterus.
HISTOPATHOLOGICAL DISCOVERIES
The histopathological findings are variable and include
erythroid with or without myeloid hyperplasia of bone marrow and passive congestion,
extramedullary hematopoiesis, follicular hyperplasia, erythrophagocytosis and
increased hemosiderin in the spleen. There may or may not be fatty degeneration
of the liver and there is centrilobular necrosis of the liver.
TREATMENT(HOW TO TREAT HAEMOBARTONELLOSIS INECTION)
In cats,20mg/kg oral oxytetracycline 8 hourly or 3 weeks.
Supportive therapy-prednisolone in severely affected cats
1-2mg/kg per os 12 hourly as required. The dosage of prednisolone should be
decreased gradually as desired as packed cell volume increases as the animal
recovers.
Blood transfusion may be needed if the packed cell volume is
less than 15%. If the cat is comatose, give parenteral glucose(dextrose
saline).
In dogs, give oxytetracycline orally, dosage is 40mg/kg per
os 8 hourly for 14 days. If relapse occurs, give 40mg/kg per os 24 hourly for
at least 30 days.
Blood transfusion is recommended if anaemia is severe and life
threatening
PREVENTION(Prevention is better than cure)
Blood sucking arthropods should be eliminated from dogs and
cats
Blood transfusion into splenectomised dogs should be avoided
The kennel and the environment should be kept clean(Environmental
hygiene is paramount).
Routine medical check up and balanced diet are recommended.
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