Gaffkaemia ( gaffkemia in American English) is a disease of , caused by the Gram-positive lactic acid bacterium Aerococcus viridans var. homari.
Discovery
Gaffkaemia was first discovered in 1947 in
(
Homarus americanus) in a holding tank in
Maine.
It was originally described as "
Gaffkya homari" by Hitcher and Snieszko, but the genus name
Gaffkya was rejected in 1971,
and the gaffkaemia bacterium was recognised as a subspecies or variety of
Aerococcus viridans by Kelly and Evans in 1974.
Effects
The effects of gaffkaemia infection include
lethargy (typically seen as a drooping tail),
anorexia and a pink colour on the ventral side of the
abdomen, which gives the disease its alternative common name of red tail disease. When lobsters are moribund, they may lie on their sides, and frequently lose
.
The effects of gaffkaemia are slowed by low temperatures, such that death can occur within two days of infection at , but can take over 60 days at .
As few as five bacteria can lead to clinical disease. When they enter the host, the bacteria colonise the heart and hepatopancreas.
Diagnosis
The classical method of
diagnosis is to culture of
haemolymph in phenylethyl alcohol broth. Cultures containing
A. viridans var.
homari change colour from purple to yellow, and form tetrads of
coccus. To reduce the four-day waiting time needed for diagnosis, a method using the indirect fluorescent antibody technique (IFAT) was developed, and, more recently, PCR-based methods have been developed.
Virulence
Gaffkaemia is
enzootic in
North America, and causes little harm to wild populations of
H. americanus. In the European or common lobster,
Homarus gammarus, however, it is far more destructive. European lobsters held in the same tanks as American lobsters can be killed within days.
A number of other crustacean species can be infected with
A. v. var.
homari, but do not develop severe disease. They include the
shrimp Pandalus platyceros, and the crabs
Cancer borealis,
Cancer irroratus,
Metacarcinus magister,
Libinia emarginata,
Chionoecetes opilio and
Chaceon quinquedens.
appear to be either immune or resistant to gaffkaemia.
Control
The primary method for controlling the incidence of gaffkaemia is improved hygiene.
Other measures include limiting damage to the
exoskeleton (preventing the bacterium's entry), reducing the water temperature, and reducing the stocking density.
may be effective against the bacterium, but only
tetracycline is currently approved by the U.S. Food and Drug Administration for use in American lobsters.
Further reading
