Problem of Mycotoxicosis in Poultry
Nischal Dutta#, Jasmine Banga*, Sidhartha Deshmukh* and Harmanjit Singh Banga*
#Department of Veterinary Pathology, Khalsa College of Veterinary and Animal Sciences, Amritsar
*Department of Veterinary Pathology, College of Veterinary Science
Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana
Mycotoxicosis term is used to imply a series of disease caused by the toxins produced by different species of fungus that grow under favorable conditions like high temperature and humidity. Different types of toxins recognized are: aflatoxins produced by Aspergillus flavus; ochratoxins by Aspergillus ochraceus; fusariotoxins by Fusarium spp.; rubratoxin by Penicillium rubrum. These toxins are known to produce different lesions in mouth and interfere with the functioning of kidneys, proventriculus, gizzard and other reproductive organs thus results in poor productivity in birds in the form of reduced egg production, thin egg shell and poor chick growth. They also hamper thiamine metabolism and causes thiamine deficiency. Mycotoxicosis is often manifested in subclinical form and therefore is very difficult to diagnose. Mycotoxicosis occur worldwide, especially in countries with high temperature and humid climate. It is known to cause widespread losses in poultry sector with high morbidity and mortality rates.
The common route of infection is by ingestion of fungal toxins that forms within feed materials that are stored improperly. Poor storage conditions, high humidity, and damage (grains) due to insects, as well as stress factors in birds potentiate the problem of mycotoxicosis. Among domestic poultry, it is duck which is most susceptible species to mycotoxins, followed by turkeys, geese, pheasants, broilers, laying hens and quail.
Some major mycotoxins known to cause toxicity in poultry species are discussed below.
Aflatoxin:
Aflatoxins are key toxins produced by Aspergillus moulds mostly in tropical regions of the world where the climate is generally warm and humid. Aflatoxins are particularly hepatotoxic and will cause tissue damage and suppression of liver proteins, which leads to negative growth rate and decreased egg productionin poultry. Aflatoxins also interfere with vitamin D metabolism, thus compromising bone and leg strength. They also weaken blood capillaries leading to the incidence of carcass bruising.
Ochratoxin:
Ochratoxin A is the most important Ochratoxin produced by different fungi and are found in temperate and tropical regions. Ochratoxin A is three times more toxic than aflatoxin to young chicks. It not only damages kidney in poultry species, but can also cause fatty liver.
Fumonisin:
Fumonisin is a mycotoxin produced by the fungus Fusarium verticillioides that is known to contaminate corn and corn products. Since, it effects maize crops which constitutes major component of poultry diet thus impacting the performance of poultry flocks. Fumonisin B1 (FB1) has been known to cause tibial dyschondroplasia in growing turkey poults.
Tricothecenes:
Tricothecene is a secondary metabolite of the Fusarium fungi, and is commonly found in grain and poultry feed. Type A Tricothecenes are known to produce more toxicity in poultry species than Type B tricothecenes. The physiological response of poultry to tricothecenes toxicity is loss of appetite, thus known as ‘feed refusal’ toxins.
Effect of multiple mycotoxin in feed and their important synergistic effects
Contaminated poultry feeds contain several mycotoxins thus exhibiting combined toxic response. As a result of synergetic toxicity clinical signs in poultry are more intense and complex when more than one mycotoxin is present in feed. These multiple contaminations rather than single mycotoxin exposure exert greater negative effects on health and productivity of the poultry flock. For this reason, clinical signs of mycotoxicosis are often severe in poultry. This may be due to synergetic interactions between different mycotoxins that exaggerate the toxicity symptoms despite of being in low individual concentrations.
Mycotoxins exhibit different clinical signs depending on the quantity of toxins as well as the type of toxin or combination of toxins present in the feed. Following clinical signs are noticed due to mycotoxicosis.
Neurotoxicity: Nervous signs showing malpositioning of wings with lack of reflexes accompanied by paralysis and incordination.
Hematopoietic effects: Bruises, haemorrhages, anaemia, pale bird syndrome (pale shanks and combs) mostly in broilers.
Gastro-intestinal involvement; Watery diarrhea, decreased feed intake, feed refusaland gizzard erosion.liver damage (jaundice).
Nephrotoxicity:Renal dysfunction with degeneration of nephrons.
Dermatological effects: Feather loss, impaired feather growth & mucous membrane defects with impaired feathering.
Hatching issues: Lower hatchability rate with increased rejection of day-old chickens
Miscellaneous: Reduced weight gain, low FCR & broiler weights. Decreased egg production, small egg size, decreased weight, and low shell quality lead to increased condemnation.
Gross pathologic changes during post mortem
Lesions vary in accordance with the type and quantum of mycotoxin ingested. Mycotoxins can cause damage to mucosal lining with which they come in contact. They can also affect blood coagulation, resulting in petechiae and ecchymotic haemorrhages in various tissues. Lesions related to aflatoxin include anemia, bile retention, scattered hemorrhages in the GI tract, skin, breast muscles along with hydropericardium, enlarged pale kidneys and fatty hemorrhagic liver. Lesions associated with trichothecenes include an inflamed GI tract, bursal and thymic atrophy, necrosis of proventriculus and gizzard, dermatitis on the shank and toes, pale bone marrow, hemorrhagic liver, gouty arthritis and pus formation in the oral cavity. Lesions associated with ochratoxin include fatty degeneration in liver with hemorrhage, pale kidneys with enlarged urates, necrosis of heart, and urate deposits on the pericardium,liver, and spleen can be noticed.
Diagnosis:
Diagnosis can be made by clinical history, clinical signs, and presence of moldy feed and final confirmation by quantification and demonstration of specific toxin in the used feed. Exposure to toxins can occur in regions where grain and feed supplements are of poor quality and storage of feed is under unhygienic conditions. Oral ulcers present on the mouth or tip of the tongue occur due to exposure to aflatoxin and mycotoxins produced by Fusarium. Definitive diagnosis can be difficult because of the rapid and high-volume use of feed and ingredients in commercial flocks. Sick poultry birds or dead birds should be submitted for testing with a sample of feed to make a diagnosis. Diagnostic tests along with necropsy should accompany feed analysis in case mycotoxicosis is suspected. Sometimes, mycotoxicosis cannot be confirmed by feed analysis but in such situation, a complete laboratory evaluation can identify the exact condition.
Treatment
The most effective treatment is neutralizing the source of toxins. Use of antifungal feed preservatives is also beneficial in preventing the toxicity. Providing proteins in the feed may also be useful in reducing mortality. Administration of selenium (0.2 ppm) and soluble vitamins, along with copper sulphate in the feed is helpful in reducing toxicity.
Prevention
- By planting fungal resistant varieties of growing plants.
- Control insect infestation through use of insecticides.
- Making planned pre-harvest, harvest and post-harvest methods.
- Reducing moisture content of plant seeds, after post harvesting and during storage.
- Storing feed bags as well as additives under low temperature wherever possible.
- Optimal use of fungicides and preservatives against fungal growth.
- Control growth of infested fungi by re-drying the products.
- Removal of contaminated seeds.
- Inactivation or detoxification of mycotoxins contaminated feeds.
- Good management along with stock control of feeders and bins, and avoiding feed spillage are of great help.
