Streptococcus & "Buyer Beware"

[Steven Sumrow]

Some of the talk from Texas Parks and Wildlife has given hope that AP system owners may soon be able to pick up and transport Mosambique tilapia instead of having to arrange for them to be delivered. This may open the door for more than just easy access for people to tilapia! This may cause the need for all of us to educate each other on the diseases that are out there and how to identify & control their effects on our systems. This happened to Me! I've had a 1200gal system that I like to use for testing new ideas. Over the last 4 years I've built many systems and changed this one in to a breeder unit. I received 60 1/2 pound fish to become my first breeder stock. Oh I was so excited, but left the new fish alone for a couple of days. I noticed upon delivery that one or two were swimming in circles. (1?) the driver dismissed it to the handling of them/stress/they always do that Bla-Bla-Blah. I closed my tanks and waited. When I looked In one of my tanks fish were still swimming in circles. I began to look over some of the fish and saw the clouding of eyes, eyes protruding, hemorrhages at the base of lips and fins, some were bolting. I tried to contact my supplier but got no response. I started to call Texas fisheries dept., Texas A&M Fisheries lab, and gathered my information for 3 more days . I talked to anyone that I could and it lead me to one conclusion. Streptococcus infection. I'm stripping my grow beds and getting ready to bleach everything from fish tanks to grow bed gravel. all fish are being disposed of and I will let it dry out for a couple of weeks. My point to all of this is that easy access to Tilapia is a great thing but watch what you buy and if you do acquire a disease clean it out don't pass it on. Many Tilapia breeders in Texas supply fish for weed control in ponds They dump them and that's all anyone ever see of them again. No one ever sees their fish die one here and there day by day.

[Scott Roberts]

A Veterinarian or Veterinarian Lab could have given you a "veterinary feed directive" for Aquaflor (medicated feed) - which would have saved most of the fish.

I can't find any research regarding the effect of Florfenicol - the active drug in Aquaflor - on Nitrosomonas or Nitrobacter species. I'd be willing to bet $5 that the nitrification cycle would continue uninterrupted, or pause/slow down during treatment and resume once treatment was concluded (10 days).

[Steven Sumrow]

Hi, Scott

I wish I could have tried to save some of these Tilapia, but this system is set up as a breeder unit and I need to stock this with  clean breeder stock. I may try to save 4 or 5 in a 100 gal unit. but that would have to be set up. The only thing is, I had more than one Texas parks & wildlife biologist and even researchers with Texas A&M fisheries lab say the best thing to do is clean, bleach everything till I feel like I got every nook and cranny and then bleach it again and let everything dry for 2 weeks.

The bottom line for me is that this unit needs to be producing 5000 of tilapia fry by march 2014. I just don't have the time or resources yet to do all the thing I'd like.

All though one of the great people at Texas A&M's lab said he would suggest me using Potassium Permanginate. Has anyone heard of treating Streptococcus with it?? Any data on any treatments would be great to have. There is some info. on treatment studies but all that I've read thus far have had poor results, Slowing death rates but after treatments end the death rate goes back up.

[Scott Roberts]

Potassium Permanganate is pretty close to bleach.  It's a strong oxidizer, and in a system laden with organics, such as an aquaponics system - it would be tough to reach treatment levels without reaching "fish kill" levels, unless you test for "permanganate demand" prior to dosing. (http://www.tandfonline.com/doi/abs/10.1577/1548-8640(1984)46%3C24%3...)

 

What i've read, suggests that it's more suited to being a disinfectant that a treatment. It should reduce transmission, but as for treatment, not so much.  (http://www.fws.gov/fisheries/aadap/PDF/Potassium%20Permanganate%20W...)

I know everybody wants "clean" breeder stock, but most fish get some degree of immunity to a disease every time they're exposed. So by treating them with antibiotics (in a vet approved manner), you're actually helping the fish to resist future problems. Plus - things like PP are an immersion treatment - antibiotics in the feed results in much lower quantities of chemicals in the water.

Just a thought

[Cecil Dale Baird]

I think you may have jump the gun with your diagnosis.  I would never assume a pathogen until I did a culture and identified it.  There are many other things that could cause the behavior your saw such as parasites.

[Steven Sumrow]

Well Cecil, it was not my diagnosis. Streptococcus is more wide spread than most people think. All of my info comes from Texas Parks And Wildlife Biologists, our State Fisheries Dept. manager and Texas A&M Fisheries Testing Labs personal that do the testing and research on these bacteria, viruses, and parasites. I think that they tend know what their talking about. I'm not trying to be rude but, it is not just their behaviour, all the signs are there. 

Cecil, You've been in the business for years what do think it is? What Parasite(Name)?

 A little Info for all of us from the "Pros" is always welcome!

 

Well Cecil, it was not my diagnosis. Streptococcus is more wide spread than most people think. All of my info comes from Texas Parks And Wildlife Biologists, our State Fisheries Dept. manager and Texas A&M Fisheries Testing Labs personal that do the testing and research on these bacteria, viruses, and parasites. I think that they tend know what their talking about. I'm not trying to be rude but, it is not just their behaviour, all the signs are there. 

Cecil, You've been in the business for years what do think it is? What Parasite(Name)?

 A little Info for all of us from the "Pros" is always welcome!

 

What causes streptococcosis in tilapia?

In farmed tilapia, the major cause of streptococcosis is Streptococcus agalactiae (including the previously described Streptococcus difficilis  / difficile, now reclassified as Streptococcus agalactiae). The closely related bacterium Streptococcus iniae can also cause streptococcosis in tilapia, but is normally not as lethal as Streptococcus agalactiae.

All species of Streptococcus are gram-positive, non-acid fast, non-motile, oxidase-positive, catalase-negative cocci.

Symptoms of Streptococcosis in tilapia

The clinical of signs of streptococcosis are very similar regardless which species of Streptococcus that is behind the disease. An infected fish will seldom display all the clinical signs listed below and it is therefore advisable to examine at least 10 fishes.

If your tilapia is suffering from streptococcosis, gram-positive cocci will be visible when impression smears of internal organs (such as liver, spleen, kidney or brain) is stained with Gram stain and examined under light microscopy at X1000 resolution.

External signs of streptococcosis in tilapia

• Infected tilapia will often develop eye lesions, e.g. endophthalmia and exophthalmia. Eye haemorrhages are common and streptococcosis can also lead to unilateral (one eye) or bilateral (both eyes) opacification of the eye. It is however possible for a tilapia to be infected with Streptococcus spp. without developing any eye lesions.
• The eyes are not the only part of the fish body where the disease can cause haemorrhages; multi-focal pin-point haemorrhages on the skin can also occur. These haemorrhages are normally located near the mouth and the base of the fins. Some tilapias become red around the anus and on the genital papilla.  
• Streptococcosis will often lead to 2-3 mm abscesses in infected tilapia. These abscesses are symmetrically positioned on the inferior jaw. In most cases, the abscesses are short lived and will soon burst and turn into haemorrhagic ulcers. Two parts of the tilapia body are prone to even bigger abscesses filled with purulent material: the base of the tail and the base of the pectoral fins. Even if the tilapia survives the streptococcosis, these big abscesses will normally remain.
• Streptococcus spp. affects the central nervous system of tilapia and infected fish can therefore engage in various forms of abnormal behaviour, such as lethargy, disorientation, swirling, and bending of the body. 
• During an acute outbreak of streptococcosis, ascites is commonly observed in tilapia. Ascites is an accumulation of fluid in the peritoneal cavity (the general abdominal cavity). Ascites is known under several different names, such as peritoneal fluid excess, hydroperitoneum or abdominal dropsy. In infected tilapia, ascites is often accompanied by a protruding anus. 

[Cecil Dale Baird]

You're probably right but to diagnose a disease by the symptoms or appearance is frowned upon by a good pathologist without a culture to identify the pathogen conclusively.

The thing about fish diseases I've observed is there are a lot of symptoms and clinical signs that are exactly the same in different diseases.

I also don't put fish and game departments on a pedestal as the final authority on anything as I've seen enough things to cause me to believe otherwise.