The poultry industry in some countries of the world is currently in a state of panic over the Avian Influenza virus. Vaccination is an alternative strategy used as a supplementary control measure during avian influenza outbreaks; however, its effectiveness can be affected by a variety of immunosuppressive agents including mycotoxins. The presence of mycotoxins in poultry rations could lead to a breakdown in vaccinal immunity and to the occurrence of diseases such as infectious bursal disease virus (IBDV) or Adenovirus. From the results of the study with mycotoxins and TOXY-NIL® Plus it can be concluded that the addition of the Fusarium mycotoxins had a significant decreasing effect on antibody (NCD) titre compared with the control group. The reduction in anti-NCD titre with mycotoxins was counteracted completely by the addition of TOXY-NIL® Plus to the contaminated feed. The results of this study indicate that the use of effective mycotoxin control offers an opportunity to significantly modify animal response to vaccination and help to improve animal health and performance.
The Mexican poultry industry is currently in a state of panic over the Avian Influenza virus which is rapidly spreading across the country. Poultry producers fear the future and comment that the situation is: “disastrous,” “the end of the industry” and “an event of historic proportions”
Outbreaks of avian influenza in cause grave economic losses and are generally controlled through extensive culling of infected birds or in some situations vaccination of affected flocks. However the latter is not without risk.
Vaccination as an important strategy for controlling viral diseases
Vaccination is an alternative strategy used as a supplementary control measure during avian influenza outbreaks; however, its effectiveness can be affected by a variety of immunosuppressive agents including mycotoxins.
Is vaccination fully effective solution?
In the case of the Mexican Avian Influenza virus, vaccination appears to be the only control strategy. Last year a local vaccine was quickly developed and distributed to halt the disease outbreak. However, in spite of a comprehensive vaccination program within the industry over 23 million commercial layers either died or were culled.
Initially it was thought that a combination of vaccination and the quarantine of infected areas had succeeded in stopping the disease. However, the H7N3 virus reappeared in January, by February it was found to be present in the broiler and breeder farms of another state and it has continued to move throughout the country since then. The vaccine is still being used in areas directly affected by the virus and in March 2013 it was also authorized for use as a prophylactic measure in many states that had not been affected by the virus.
To compound this serious industry problem the efficacy of the vaccine itself is also in doubt. Poultry veterinarians and producers expressed their doubts about efficacy in the question and answer session following a routine presentation about the vaccine and its production by a government veterinarian. Producers and veterinarians commented that they did not believe that the vaccine is working like it should and suggested that perhaps in some instances the immune system of some birds is not responding to the vaccine
What is the role of mycotoxins in vaccination failure?
Avian mycotoxicosis is considered to be one of the most important problems in the poultry industry. It causes severe losses not only in terms of lost performance, but also as an immunosuppressive agent increasing the bird’s susceptibility to diseases and mortality.
It is well known that immunity acquired through vaccination can be impaired by ingestion of mycotoxins. The Egyptian study of Hegazy el al. (2011) revealed that mycotoxicosis might be the cause of vaccination failure against Avian Influenza virus.
Mycotoxin induced immunosuppression may be manifested as depressed T- or B-lymphocyte activity and suppressed production and impaired macrophage/neutrophil-effector functions (Hatori et al., 1991). Mycotoxins reduce the level of antibodies following infection or vaccination, and reduce the activity of phagocytic cells.
Suppressed immune function by mycotoxins can eventually decrease resistance to infectious diseases, reactivate chronic infections and/or decrease vaccines efficacy (Oswald et al., 2005). Therefore, the presence of mycotoxins in poultry rations could lead to a breakdown in vaccinal immunity and to the occurrence of diseases such as infectious bursal disease virus (IBDV) (Somvanshi and Mohanty, 1991) or Adenovirus (Shivachandra et al., 2003). Low levels of toxins, below observable overt toxicity, in rations are also likely to alter normal immune functions.
Deoxynivalenol (DON) can modulate immunological parameters. Determination of serum titres of antibodies against New Castle Disease (NCD) after regular vaccination is a method which can be used to evaluate immuno-modulating effects of certain mycotoxins in vivo.
Table 1 - Anti-Newcastle disease (NCD) titers of broilers at day 42 for the different treatments.
Different letters in one column indicate statistically significant differences (P≤0.05).
From the results in table 1 it can be concluded that the addition of the Fusarium mycotoxins had a significant decreasing effect on anti-NCD titre compared with the control group. The supplementation of a mycotoxin deactivation product without mycotoxins did not result in a change of NCD-antibodies versus the level in the control group. The reduction in anti-NCD titre with mycotoxins was counteracted completely by the addition of mycotoxin deactivation product to the contaminated feed.
The results of this study indicate that the use of effective mycotoxin control offers an opportunity to significantly modify animal response to vaccination and help to improve animal health and performance.
- Hatori, Y., Sharma, R.P. and Warren, R.P. (1991). Resistance of C57B1/6 mice to immunosuppressive effects of aflatoxin B1 and relationship with neuroendocrine mechanisms. Immunopharmacology 22: 127-136.
- Hegazy, A.M., Abdallah, F.M., Abd-El Samie, L.K., and Nazim, A.A. (2011).The relation between some immunosuppressive agents and widespread nature of highly pathogenic avian influenza (HPAI) post vaccination. Journal of American Science, 7 (9).
- Oswald, I.P., Marin, D.E., Bouhet, S., Pinton, P., Taranu, I., and Accensi, F. (2005). Immunotoxicological risk of mycotoxins for domestic animals, Food Additives & Contaminants: Part A, 22:4, 354-360.
- Shivachandra, S.B., Sah, R.L., Singh, S.D., Kataria, J.M., and Manimaran, K. (2003). Immunosuppression in broiler chicks fed aflatoxin and inoculated with fowl adenovirus serotype-4 (FAV-4) associated with hydropericardium syndrome. Vet. Res. 27 Issue PP. 39-51.
- Somvanshi, R. and Mohanty, G.C. (1991). Pathological studies on aflatoxicosis, infectious bursal disease and their interactions in chickens. Indian J. Vet. Pathol. 15:10-16.