Author | Liang Zhiyuan Hu Fei Chen Siruo Hu Xiong Live Baoyuan Fish Disease Room
The pathogens of fish diseases ----- the biological characteristics of viruses, bacteria, fungi, parasites, etc. are very different, and their sensitivity to drugs is very different, and the treatment ideas and medication schemes are completely different.
Even raw fish (snakeheads, hybrids), which are extremely tenacious and are known for "floating heads for three days without dying", are also plagued by bacterial diseases such as Schubert's aeromonas and Nocardiosis in the hot summer every year.
Although "prevention is the mainstay, prevention is more important than treatment, and prevention and control are combined" is the policy of fish disease prevention and control, and the theories, strategies, and products (programs) on fish disease prevention in the industry are not numerous, but the bacterial diseases in the front line of breeding are still prevalent every year, and a large number of farmers suffer heavy losses every year. What should we do in the face of the surging fish bacterial disease?
This article is based on a typical case to talk about the understanding and thinking of the diagnosis and treatment of fish bacterial diseases, I hope to be helpful to everyone, welcome to leave your insights in the comment area!
First, the general situation of the disease
In June 2021, in Guangzhou, Guangdong Province, a farm has 6 ponds, all of which are farmed raw fish (hybrid fish), and their basic information is as follows:
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Pond number
Water
depth
Number of ponds
Storage pond weight
1 #
7 acres
2 meters
60,000 tails
120,000 pounds
2 #
40,000 tails
80,000 pounds
3 #
4 acres
25,000 tails
50,000 pounds
4 #
30,000 tails
45,000 pounds
5 #
11 acres
120,000 tails
156,000 pounds
6 #
70,000 tails
135,000 pounds
On 15 May, dead fish began to appear in individual ponds of the farm, with symptoms such as white spots (nodules) on the flower body and internal organs.
On May 20, the owner of the pond collected the sick fish and sent them to the live Baoyuan fish disease room for testing, and after being diagnosed with Schubert aeromonas, he followed the recommendations and took the drug continuously for 3 days, but saw no obvious effect, and the owner of the pond switched to bile acid and tri-yellow Chinese medicine for conditioning.
On 30 May, the number of dead fish increased further and disease began in other ponds.
On June 1, the owner of the pond sent the sick fish to a nearby pharmacy for testing, was diagnosed with Nocardiosis, and issued a Nocardi course for treatment, mixed with medicine for 4 days, the dead fish did not decrease but increased, and the daily loss increased to more than 300. The owner of the pond also sent the sick fish to another pharmacy for testing, was diagnosed with bullet virus disease, so he took measures such as stopping the material, changing the water, detoxification and anti-stress treatment, and by June 15, the condition had not improved, and he was again sampled and sent to the huobaoyuan fish disease room for comprehensive testing.
2. Laboratory testing
The owner of the pond only sent for examination for more serious disease and
In appearance, there are a small number of spotted or needle-like bleeding foci on the surface of the sick fish, and the vitality is very weak (P01, 02); the gill filament is basically ruddy and there is no obvious abnormality (P03); anatomy, a large number of fine white dots (nodules) (P04~06) can be seen in the liver, spleen, kidneys, etc.; the stomach and intestines are obviously hyperemic and red (P07).
■P01,02 A small number of spotted/pinniped hemorrhagic foci on the surface of the diseased fish
■ Left: P03 the gills of the diseased fish are ruddy; Right: P04 shows the white spots of the liver
■ Left: P05 shows the spleen fine white dots; right: P06 shows the kidney fine white dots;
■ P07 Shows obvious redness of the intestine;
Sequentially cut an appropriate amount of gill filament and scrape the mucus of the body surface lesion to make a water-soaked tablet, which was observed under a light microscope and was not seen. Aseptic operation, take the kidney tissue of the diseased fish inoculated in the brain heart immersion agar medium, 30 °C constant temperature culture for 24h, all have a large number of round, fine, light yellow gray, take it for Gram staining, microscopic examination, the body is short rod-shaped, combined with experience, the preliminary judgment is Schubert aeromonas; after purification of the drug susceptibility test (paper method), the results show that 2 strains are highly sensitive to The No. 1 antibacterial drug, and are common to florfenicol, doxycycline and other common
■ P08 No parasites are seen in gill filaments
■ Left: P09 shows the visceral culture to a large number of bacteria; right: P10 shows the morphology of bacteria after Gram staining
■ P11,12 Indication drug susceptibility test
Strains / antibacterials
Bacteriostatic circles (φ,cm)
numbering
1
2
3
4
5
2106151
b-S
2.5
1.3
1.2
1.15
2106152
a-S
3. Treatment plan and effect
Combined with laboratory testing and diagnosis and treatment experience, it was preliminarily judged that the 2 ponds of raw fish examined were all Schubert aeromonas. After exchanges, the owner of the pond said that the condition and symptoms of his 6 ponds were highly similar, so it was recommended that all of them be treated according to Schubert's aeromonas. Considering that the owner of the pond has disinfected the water body after changing the water, it is recommended that he choose sensitive antibiotics (Antibiotic No. 1) with mixtures such as vitamin K3 to feed.
On the morning of June 20, the owner of the pond reported that he had been using the above internal medication scheme for 4 days, and the amount of dead fish had not decreased but increased, from 161 / day at the beginning of the mixing to 200 / day, ready to give up treatment. After communication analysis, it was found that the feeding amount of the farm was seriously low when mixing drugs, and the total loss did increase slightly, but the average feeding rate of the 4-day feeding was less than 0.25%, and the number of dead fish did not decrease but increased; while the average feeding rate of the 4-day was slightly higher, between 0.46% and 0.60%, and the condition remained stable or slightly improved.
■ Figure 13, 14 pond master recorded daily feeding and loss data
■Fig. 15-20, based on the data analysis of Fig. 13-14, it can be seen that ponds with higher feeding rates have obvious curative effects.
After repeated communication, under repeated requests, the owner of the pond agreed to continue taking the drug for 4 days (appropriate increase in medication). On June 30, the owner of the pond feedback, in accordance with the recommendation to continue to use the drug, the number of dead fish decreased rapidly, in addition to the feeding rate of the seriously low 1 # pond there are still 11 dead fish, the remaining 5 pond loss is basically cleared, the customer is very recognized by the efficacy of the program!
Fourth, the understanding and thinking of the diagnosis and treatment of fish bacterial diseases
The factors that cause fish diseases can be divided into two categories: biological pathogens and non-biological pathogens, the former can be divided into viruses, bacteria, fungi, parasites and so on. According to relevant surveillance statistics, the proportion of fish diseases caused by bacterial infections is the highest, reaching about 45%. The warm climate of the Pearl River Delta region and the epidemic of bacterial diseases almost all year round pose a huge threat to the aquaculture industry; even raw fish (snakeheads, hybrids) that are extremely tenacious and known for "floating heads for three days without dying" are also plagued by bacterial diseases such as Schubert aeromonas and Nocardiosis in the hot summer every year. Although "prevention is the mainstay, prevention is more important than treatment, and prevention and control are combined" is the policy of fish disease prevention and control, and the theories, strategies, and products (programs) on fish disease prevention in the industry are not numerous, but the bacterial diseases in the front line of breeding are still prevalent every year, and a large number of farmers suffer heavy losses every year. What should we do in the face of the surging fish bacterial disease? Combined with this case, looking back at many years of experience in the diagnosis and treatment of fish diseases, the author believes that there are the following points.
4.1 Accurate diagnosis is a prerequisite
The pathogens of fish diseases ----- the biological characteristics of viruses, bacteria, fungi, parasites, etc. are very different, and their sensitivity to drugs is very different, and the treatment ideas and medication schemes are completely different. For example, for viral diseases, there is no effective treatment drug, and water disinfection should be carried out with stress mitigation and mild disinfectants to prevent further deterioration of the disease and minimize losses; for bacterial diseases, it is necessary to treat them by using efficient disinfectants and internal feeding of sensitive antibiotics; and for body surface parasitic diseases, water insecticide is the mainstay. Accurate diagnosis, especially accurate judgment of the main pathogens, and selection of correct treatment ideas are the prerequisites for effective treatment. For example, in this case, the owner of the pond blindly stopped the material, changed the water, or treated according to the idea of bullet virus disease in the early stage, but did not obtain obvious curative effect, and the condition gradually worsened.
For most bacterial diseases, it is difficult to accurately judge based on the appearance of symptoms and tools such as microscopes, and bacterial isolation and culture are required to confirm the diagnosis.
4.2 Choosing the right medicine and choosing a good drug is the key
The types of fish pathogenic bacteria are very rich, and the sensitivity of different types of pathogenic bacteria to drugs varies greatly; even if the same bacteria are affected by region and medication history, the sensitivity to drugs will be significantly differentiated. Bacterial isolation and culture, screening out sensitive antibiotics by paper susceptibility test, and measuring their effective bacteriostatic concentration and effective sterilization concentration by test tube method have a very critical guiding role in treatment. For example, neither Nocardia eels norcans and Schubert aeromonas can cause white spots (nodules) in the liver, spleen, kidneys, etc. of raw fish, but the sensitivity of the two to common fishery antibiotics varies greatly, most nocardia anchovy are more sensitive to doxycycline, while most Schubert aeromonas are highly resistant to doxycycline, in this case, the owner of the pond also mixed with the so-called Nocardia package, but failed to control the disease. Pathogenic bacteria isolation and susceptibility testing, screening of sensitive antibiotics, can greatly improve the success rate of treatment.
Secondly, while choosing the right type of drug, it is also very important to choose the quality of the drug. Although sensitive antibiotics can be screened out by susceptibility tests and effective bacteriostatic concentrations can be determined, because the drug susceptibility tablets and antibiotic raw powders used in the industry for drug susceptibility testing are standard products or need to be calibrated, their quality is far from being comparable to cheap inferior drugs and "three noes" products on the market. We recommend that even if a susceptibility test is done, a reliable quality national standard drug should be selected.
4.3 Thorough implementation of the medication regimen is the guarantee
Accurate diagnosis, selection of the right medicine, selection of good medicine, the success of the treatment of bacterial diseases has completed ninety-nine steps, but there is still one step, easy to ignore the step, that is, the thorough implementation of the drug regimen. On the one hand, the causes of fish diseases are very complicated, some fish diseases are difficult to treat, some fish diseases have a variety of programs, no fishing doctor can 100% cure fish diseases, many farmers do not trust the fishery doctors 100%; on the other hand, for many farmers, farming is related to a year's harvest, when encountering major diseases, it is easy to be anxious, panic, and then indiscriminate use of drugs, blind use of drugs; Moreover, in recent years, some manufacturers have sold their own products in the name of promoting breeding technology, and have spread a large number of patchwork, Wrong knowledge of disease prevention and control interferes with farmers' cognition, and so on. Due to these effects, farmers often do not have enough thorough or unauthorized changes in the implementation of medication prescriptions issued by fishery doctors, which greatly reduces the efficacy. As in this case, in mid-May, the disease has been accurately diagnosed as Schubert aeromonas in our fish disease room, but the owner of the pond only gave up the use of drugs for 3 days and switched to other programs, and finally dragged on for a month, tried various treatment plans, and finally found our diagnosis again; the owner of the pond used our program for the second time to treat the 4th day, did not see a significant reduction in loss, and wanted to give up the treatment, after we collected its data for careful analysis, the owner of the pond still lacked confidence, asked for a reduction in medication, after repeated communication, The owner of the pond is willing to strictly implement the treatment plan according to the requirements of our company, and finally obtains good efficacy and effectively controls the disease.
The diagnosis and treatment of fish diseases is a very high work with high experience and technical requirements, in addition to the three points mentioned above, many factors such as weather, water quality, substrate, feeding and so on will also have a huge impact on the efficacy. Overall, most bacterial diseases in fish can be cured, and the success rate of treatment can be greatly improved by bacterial culture and susceptibility testing. The author believes that an excellent fishery doctor should always keep learning, rationally apply professional instruments and equipment, improve diagnostic ability, screen effective drugs, and improve the effectiveness of prescribing; should also diligently summarize which fish diseases can be cured, can be cured in a few days, which fish diseases are difficult to treat, how to reduce losses, continuously accumulate experience, improve the ability to predict the efficacy, enhance customer confidence; when prescribing, it is necessary to put the efficacy in the first place, refuse some unreasonable requirements of farmers when necessary, and fully communicate with farmers. Ensure that the programme is thoroughly implemented. Of course, as a farmer, we must also strengthen the study of breeding knowledge, learn to distinguish some wrong "knowledge", believe in science, and believe in professionalism. When the scientific treatment plan is thoroughly implemented, the bacterial disease can be quickly controlled, and this requires the joint efforts of fishermen and farmers.