White Spot Disease in Penaeus Shrimp
White Spot Disease is a serious viral infection affecting the caramote shrimp (Penaeus kerathurus), a species farmed or caught in the Mediterranean Sea, particularly in Tunisia. It is caused by a virus known as White Spot Syndrome Virus, or...
What is it?
White Spot Disease is a serious viral infection affecting the caramote shrimp (Penaeus kerathurus), a species farmed or caught in the Mediterranean Sea, particularly in Tunisia.
It is caused by a virus known as White Spot Syndrome Virus, or WSSV.
This virus is considered one of the most dangerous threats to shrimp farms worldwide, as it can kill nearly an entire pond within days.
Key point
This disease is considered one of the most devastating for shrimp farms worldwide, with mortality potential approaching 100% within days. It is subject to mandatory surveillance and reporting to the competent health authorities in many countries.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
The most recognizable sign is the appearance of small, round white spots under the shell, most visible on the head and back of the animal.
However, these white spots are not always present or visible to the naked eye, especially early in the disease.
Infected shrimp become soft, swim abnormally, gather near the water surface or the edges of the pond, and stop eating.
The shell may separate from the flesh more easily than normal.
In the most severe forms, which are also the most common, the animals die suddenly and in very large numbers, sometimes within two to seven days after the first signs appear.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by White Spot Syndrome Virus (WSSV), a DNA virus that infects only crustaceans, particularly penaeid shrimp such as the caramote.
The virus attacks many tissues in the animal, which explains the speed and severity of the disease.
Intensive shrimp farms with high stocking density are particularly vulnerable, as the virus spreads rapidly in these settings.
Abrupt changes in water temperature, salinity, or water quality (oxygen depletion, pollution) stress shrimp and create conditions favoring the disease.
Introduction of new shrimp or larvae without prior health screening is a major risk factor.
The presence of wild crustaceans carrying the virus around farm ponds also increases contamination risk.
Transmission
The virus spreads very easily from one shrimp to another, either through direct contact or contaminated water.
It can also spread through consumption of an already infected or dead shrimp, including among shrimp in the same pond (cannibalism).
Birds, nets, farming equipment, water from a neighbouring pond, or even larvae and shrimp introduced into a farm can carry the virus from one site to another.
Stress, for example from sudden changes in temperature or salinity, promotes the disease to appear in animals already carrying the virus.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis cannot be confirmed by observation of white spots alone, as other conditions can produce similar signs.
It relies on specialized laboratory testing, particularly molecular biology techniques to detect viral DNA in shrimp tissues.
These analyses are performed by veterinary laboratories or official aquatic animal health services.
In the event of abnormal mortality in a farm, a professional or the competent animal health authorities must be informed promptly.
Treatment
Currently, no effective curative treatment exists for this viral disease.
Management consists essentially of limiting spread: isolation of affected ponds, cessation of water exchange, and in some cases, controlled destruction of sick animals to protect the remainder of the farm and neighboring operations.
Supportive measures, such as improving water quality, can sometimes limit the extent of losses, though they do not cure already-infected animals.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no vaccine or curative treatment available for this disease.
Prevention relies primarily on strict biosecurity measures at farm entry points: health screening of larvae or juveniles before introduction, quarantine when possible, and equipment disinfection.
It is important to restrict uncontrolled water exchange between ponds or with the natural environment, and to avoid introducing animals or water from unknown health sources.
Good water quality management (stable oxygen, temperature, and salinity levels) and reasonable stocking density reduce animal stress and therefore vulnerability.
Regular pond monitoring allows early detection of any suspicious signs and action before the disease spreads on a large scale.
Possible complications
The major complication is rapid and massive mortality affecting an entire pond or farm operation, with very significant economic consequences for producers.
The disease can also spread to neighboring farms or the natural environment, threatening wild populations of shrimp and other crustaceans.
When to see a veterinarian
Unusual or massive mortality in a shrimp farming pond.
Presence of white spots under the shell associated with abnormal shrimp behavior (lethargy, clustering at the surface).
Sudden cessation of feeding throughout all or part of a pond.
Any suspicious sign before introducing new animals into an existing operation.
Prognosis
The prognosis is very poor once the disease appears, with mortality rates potentially reaching nearly all animals in a pond within a few days.
No recovery is possible for infected animals.
Only early detection and strict biosecurity measures allow losses to be limited across a farm.
Frequently asked questions
Is this disease dangerous for humans?
No. The virus responsible only infects crustaceans such as shrimp. It poses no risk to human health, including if consuming animals from affected farms after health inspection.
Can white spot disease in shrimp be treated?
No, there is no curative treatment. Management aims solely at limiting the spread of the disease to other animals and ponds.
How to protect a shrimp farm against this disease?
The best protection relies on strict biosecurity measures: health screening of introduced animals, stable water quality, limitation of uncontrolled water exchanges, and regular monitoring of ponds.
Are white spots always visible in sick shrimp?
No, they are not systematic nor always visible to the naked eye. A definitive diagnosis requires specialized laboratory tests.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 27 October 2026
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