Prawn Diseases, Prevention, and Control
Are you aware that the most dreaded thing that can happen to any prawn farmer is prawn diseases?
Prawns can be affected by several microorganisms such as bacteria, viruses, fungi, parasites, and even algal toxins. Moreover, prawns can be infected with disease prawns for the following reasons:
- Nutritional deficiency
- Poor water conditions [and]
- Environmental pollutants.
Diseases In Prawn Hatcheries
Necrosis of Appendages
It is important to note that Bacteria could attack when there’s a physical damage to the appendages. Exoskeleton and tips of the appendages in affected larvae begin browning thereby making them look eroded and opaque.
However, regular pathogenic bacteria via standard microbiological patterns can identify the disease. More so, Isolation, improved water quality and optimal stock densities would aid in control and prevention.
Just as the name implies, an infected larvae glow in darkness – and is one of the terrible diseases resulting in heavy mortality. Although, based on their biochemical and morphological characteristics, such disease can be identified.
In order to control this disease, UV sterilized water and chlorination (Ca(ClO)2 200ppm for 60 mins) must be used.
Filamentous Bacterial Disease
In addition, an Infected prawn larvae may show fouling of appendages, gills, and its body surface. Also, the larva may die of hypoxia. Based on signs and symptoms, it is recommended to administer copper sulphate bath treatment [0.25 – 1 ppm for 4 to 6 hours].
This is a highly susceptible fungal disease to Zoea and Mysis larva. Infected larva may appear opaque, and within a day or two, the entire stock larva could die. The effective control for this is by giving Treflan (0.1 to 0.2 ppm) bath for one day to the infected larva
Diseases in Juveniles and Adult Prawns
MonodonBaculovirus (MBV) Disease
MBV is a viral disease which affects both postlarvae and adults prawns. Infected prawns are quite lethargic with the surface and fouling of gills. Most especially, this disease has very high death rates.
Unfortunately, there is no medicinal cure, although it can be controlled by simply using MBV-free stock. Affected prawns must be burnt or/and buried soon after mixing with lime away from the farm.
Brown Spot Disease
This disease can be otherwise called a shell or rust disease – which is caused by bacteria. The body surface of the affected prawns may show brown or black eroded patches. When the symptoms occur, confirmation of this disease is done using standard microbiological strategies. Above all, Infected prawns are fed with antibiotic fortified feeds [1.5g Oxytetracycline per kg feed] for at least two weeks.
Bacterial septicemia, otherwise referred to as Vibrio disease is caused by bacteria. This disease can be seen if the prawns are lethargic with unusual swimming behaviour.
However, In severe cases, the gill covers occur flared up most times extensively melanized black blisters right on the abdomen region.
Well, as regards to the treatment; Infected prawns are fed with antibiotic fortified feeds [1.5g Oxytetracycline per kg feed at 2 – 10 percent of body weight] for about two weeks.
White Spot Disease [WSD]
WSD is caused by virus SEMBV. The infected prawns do swim to the surface area of the water, and accumulate near the pond dikes.
The following are its Physical signs or symptoms: white patches or spots on the shell and abdomen regions. Unluckily, there has been no verifiable cure for this disease.
Being a prawn farmer is not an easy task, you must however be very observant to the physiochemical changes in your prawn hatchery or pond, so as to ensure you are very far away from incurring any lose.