Real hazards of mycotoxins in poultry and public health

Mycotoxins are secondary metabolites produced by heterogeneous fungi. When present in animal and human feed, they can act on the organism, impairing performance and causing pathological changes called mycotoxicosis.

These toxins can have a negative impact on animal production affecting health and productivity levels. Therefore, it is crucial to understand how different types of mycotoxins influence the health of birds in order to control and prevent economic losses.

Several epidemiological studies in humans have shown that the presence of mycotoxins in food, especially aflatoxins, can be quite harmful and may even be the cause of liver tumors.

Monitoring the genuine risks linked to the presence of these toxins in the food chain, particularly in milk, meat, and eggs, is crucial and falls under the collective responsibility of all stakeholders engaged in production, with health authorities playing a significant role.

Mycotoxins also affect various bird species with varying degrees of susceptibility.

Ducks, geese, and turkeys are more susceptible than broiler chickens.

It is also worth noting that the presence of mycotoxins in the early stages of bird life is always the most concerning.

According to recent studies, the presence of DON, for instance, can cause significant harm during the later phase of intestinal growth, specifically between 18 and 25 days, thereby impacting performance closer to the final fattening stage.

Classes of Mycotoxins

The most important mycotoxins are aflatoxins, ochratoxins, zearalenone, T-2 toxin, and fumonisins.

There are 6 main mycotoxin classes:

• Aflatoxins (Aspergillus spp)
• Ochratoxins (Aspergillus spp)
• Trichothecenes (Fusarium spp.)
• Fumonisins (Fusarium spp.)
• Zearalenone (Fusarium spp.)
• Ergot Alkaloids (Claviceps spp.)

In poultry production, the main interactions and factors that can influence mycotoxicosis are:

Farm management, highlighting factors such as hygiene, humidity, and temperature;

• Exposure time
• Age, sex, species
• Nutrition and the health level of the birds
• Mycotoxin type and concentration level
• Other co-occurring toxins

While mycotoxins can elicit various effects, a shared characteristic among them is their ability to induce immunosuppression and compromise the overall immune system of birds.

Various recent studies confirm that broilers are sensitive to the presence of Fusarium spp. mycotoxins. and the presence of these mycotoxins at moderate levels negatively impacts appetite and hampers growth performance, particularly during the growth stage.

Aflatoxins

It is one of the main and most frequently found mycotoxin in animal production.

Clinical signs in birds:

• Reduced feed intake
• Weight loss
• Decreased egg production
• Mucosal paleness
• Loss of leg and beak pigmentation
• Increased hematomas
• Immunosuppression
• Increased mortality

Observed lesions:

Liver lesions are some of the most common. They are characterized by organ enlargement, friability, paleness, and marked fat infiltration.

Increased size of the spleen and kidneys.

Reduced size of the bursa of Fabricius and thymus.

Hemorrhages and petechiae in muscles (decreased coagulation factors and increased capillary fragility).

Carcinogenic and teratogenic changes. These can present themselves as acute or chronic conditions.

Bird liver with lesions associated with aflatoxicosis.

Ochratoxin A (OTA)

Clinical signs in birds:

• Reduction in weight gain
• Depression
• Dehydration
• Decreased egg production and hatchability rate.
• Surviving animals are stunted, have poor plumage, anemic, and immunosuppressed.

Lesions observed in necropsy:

Enlarged kidneys, white to yellowish in color (with white foci of urate crystals)

Urate deposition on pericardial, perihepatic, peritoneal, and articular surfaces.

In surviving birds:

• Due to renal compensation, the kidneys appear enlarged, fibrotic, and pale.
• Fatty liver
• Decreased size of the bursa of Fabricius and thymus with subsequent immunosuppression.

Bird kidneys with lesions consistent with the presence OTA.

Trichothecenes

The clinical signs in birds ingesting abnormal levels of trichothecenes, mainly T-2 toxin, are:

• Reduced appetite
• Reduced weight gain
• Diarrhea (hemorrhagic)
• Anemia
• Poor plumage

Oral lesions, decreased egg production, decreased shell quality, and hatchability rate are all observed in adult birds.

These lesions are highly characteristic:

• Ulcers in the corners of the mouth
• Hard palate
• Cleft palate and dorsal surface of the tongue (3-4 days after ingestion)
• Decreased size of the bursa of Fabricius and thymus
• Anemia
• Pale bone marrow

Compatible lesions with T-2 toxin presence.

Fumonisins

Due to the significance of corn as a fundamental ingredient in bird nutrition, particular emphasis is placed on fumonisins.

Most common clinical signs:

• Reduced feed intake
• Decreased weight gain
• Diarrhea

The observed lesions are more nonspecific:

• Catarrhal enteritis
• Hepatomegaly
• Possible enlargement of the kidney, pancreas, proventriculus, and gizzard
• Decreased size of the bursa of Fabricius and thymus
• Anemia
• Pale bone marrow

Zearalenone

The presence of these mycotoxins in birds can affect the reproductive system. Therefore, their importance is greater in adult birds, where secondary sexual characteristics are more evident and can cause thickening of the cloacal mucosa.

Differential diagnosis of mycotoxicosis in birds

• Aflatoxicosis: Gumboro disease, fatty liver syndrome, malabsorption syndrome, and amyloidosis.
• Ochratoxins: Aflatoxicosis, visceral gout, infectious bronchitis, sodium poisoning, water deprivation, vitamin A deficiency, and malabsorption syndrome.
• Fusarium toxins: Avian pox (wet form), vitamin A deficiency, trichomoniasis, ochratoxicosis, aflatoxicosis, bird dropping disease, and Gumboro disease.

How do mycotoxicosis in birds affect public health?