| A hemolytic, sometimes febrile, disease is caused by rickettsiae of the genus
Eperythrozoon
of the family Rickettsiaceae. Based on phylogenetic similarities, several members of the genus
Eperythrozoon
have recently been transferred to the genus
Mycoplasma
. Cats (
Haemobartonella
[Eperythrozoon]
felis
, see
hemobartonellosis,
Hemobartonellosis), dogs (
E
canis
), cattle (
E
wenyoni
,
E
tegnodes
,
E
tuomii
), sheep and goats (
E
ovis
), and pigs (
E
suis)
, can be infected. Except for sheep and goats, each
Eperythrozoon
sp
is host specific. Members of the genus have a worldwide distribution. Disease is often subclinical with a mild anemia, but stress in animals may result in severe clinical symptoms. |
| Etiology and Transmission: |
|
Eperythrozoon
spp
are transmitted mechanically by arthropods.
H
felis
is also transmitted in utero. Transmission may occur via surgical procedures through blood contamination of instruments (eg, Mules operation in sheep, needle contamination during vaccination). Lice are the main method of transmission in pigs, but fleas and mosquitos may also cause transmission in cats, sheep, and goats. Ticks are vectors for dogs (
Rhipicephalus
sanguineus
) and cattle. |
|  |
| Clinical Findings and Lesions: |
| Eperythrozoonosis in cattle, dogs, and goats is regarded as an innocuous disease and usually causes only mild anemia. Animals with clinical disease have inappetence, wasting, anemia, malaise, and depression. Body temperature may be elevated but is often normal. Cats with eperythrozoonosis (feline infectious anemia) show pallid mucous membranes and tongue. The spleen can be enlarged and palpable through the abdominal wall. Pigs show fever, staggering or paralysis, paleness of
mucous membranes, emaciation, and jaundice. Reproductive failure, weakness in piglets, and ill thrift can be indicative of eperythrozoonosis. Disease in sheep is evident as ill thrift in lambs and weaners; signs are similar to those in pigs. |
| Hematology shows a macrocytic hemolytic anemia, with anisocytosis, poikilocytosis, and a marked left shift in erythrocyte maturation. The leukocyte count is normal or slightly elevated. |
| |
| Diagnosis: |
|
Eperythrozoon
spp
are usually coccoid (0.5-1.0 µm diameter). In Giemsa-stained peripheral blood smears, they appear attached to the surface of erythrocytes. Occasionally, rod-shaped forms (1-3 µm diameter) can be seen. It is important to differentiate between acute disease, in which the organism is readily identified in peripheral blood smears, and chronic, subclinical disease, in which animals present with a secondary infection and the organism can be difficult to detect in blood
smears. |
| |
| Treatment and Control: |
| In severely affected animals, especially cats, transfusion may be required before treatment can begin. Tetracyclines used at recommended dose rates have proved effective. The use of arsenical-based drugs is no longer permitted in many countries. |
| Treatment of sheep in flock management practice is not recommended because infected animals develop immunity if supported with good nutrition during the hemolytic crisis, whereas treatment results in a loss of immunity and clinical disease on reinfection. The use of disposable needles and correct sterilization of surgical instruments will minimize accidental transmission. Control of arthropod parasites on pets and pigs is recommended. |
| |
| Zoonotic Risk: |
| Recent reports from Inner Mongolia, China, suggest that
Eperythrozoon
spp
may be zoonotic, with evidence of congenital transmission. The prevalence in humans appeared to be associated with occupation, but there was also seasonal variation. Up to 35.3% of some populations were shown to be infected. The infections were mild except for pregnant women and their children. All of the children of pregnant women were shown to have
Eperythrozoon
spp
in their peripheral blood and umbilical cord. |
| |
;)