Reports of discolored and diseased shrimp in the northern Indian
River Lagoon in 2005 pointed researchers to the source of
Scientists' identification of a microscopic parasite affecting
pink shrimp (Farfantepenaeus duorarum) illustrates how the
public can assist marine research by reporting unusual
In February 2005, people in the Titusville and Melbourne area
began noticing shrimp with a purplish discoloration of the shell
and large white visible masses in the flesh, thought to be cysts or
tumors. Numerous reports from shrimpers and others prompted an
investigation by biologists with the FWC's Fish and Wildlife
Research Institute. Some observers sent specimens of affected
shrimp from the northern Indian River Lagoon.
By microscopically examining the samples, biologists identified
the cause: a parasite called microsporidia, which can affect
several species of shrimp. The parasite invades the blood system
and tissues surrounding the intestine and multiplies there until it
eventually destroys and replaces muscle tissue, creating opaque
white patches under the shell. The cottony appearance of the
abdomen gives the common name to this disease: "cotton" or "milk"
shrimp. Dark discoloration of the shell also occurs when pigmented
cells react to the parasite's presence by expanding or increasing
Infected shrimp can become weakened or paralyzed and thus more
susceptible to other diseases and predators. In aquacultured
shrimp, heavy infections of the parasite in the muscle can render
the product unmarketable.
This parasite in shrimp is not considered a risk to human
consumers; however, the Florida Department of Health advises
common-sense precautions against eating any catch that is obviously
weakened by infection. Diseased shrimp should be buried or
otherwise disposed of away from the water rather than tossed back.
Microsporidia are also known to infect fish, which could be other
hosts in the shrimp parasite's life cycle.
Though reports of this disease in Indian River Lagoon shrimp
tapered off the following year, reports from shrimpers in the fall
of 2010 alerted the FWC to the presence of a nonnative species of
shrimp, the tiger
prawn, in the area. Researchers encourage the public to report
all findings of abnormal shrimp to the FWC's Fish Kill Hotline,
Figure 1: White opaque patches
appear under the shell of shrimp infected by microsporidia.
Figure 2: The masses are not tumors
or cysts, but hundreds of microscopic parasites.
Figure 3: The parasite
can invade the muscle tissue and surrounding organs, appearing as