Avian Mycotoxicosis in Developing Countries

Avian mycotoxicosis refers to all the diseases caused by the effect of mycotoxin in birds. These diseases may not be pathognomonic and sometimes subclinical and difficult to diagnose. The problem is worldwide but effort will be made to localise the effect of these diseases in developing countries. Developing countries have more than 50% of total meat and egg production in global poultry market: [1]. The global poultry meat market is 86.8 million tonnes, consisting of chicken: 85.6%, turkey: 6.8%; duck: 4.6%; goose and guinea fowl: 2.6%.


Introduction
Avian mycotoxicosis refers to all the diseases caused by the effect of mycotoxin in birds.These diseases may not be pathognomonic and sometimes subclinical and difficult to diagnose.The problem is worldwide but effort will be made to localise the effect of these diseases in developing countries.Developing countries have more than 50% of total meat and egg production in global poultry market: [1].The global poultry meat market is 86.8 million tonnes, consisting of chicken: 85.6%, turkey: 6.8%; duck: 4.6%; goose and guinea fowl: 2.6%.The world market poultry meat and egg market is been influenced by the production and managemental style from the developing countries.Avian mycotoxicosis is a great constraint in poultry industry, because the disease is characterized by immunosuppresion, hepatotoxicity, nephrotoxicity, loss of egg production, mutagenicity and tetratogenicity.
Mycotoxin are antinutritive factor present in feed ingredients and in concentrated feed, they are a group of secondary fungal metabolites of low molecular weight, diverse and ambiguous in nature, which are specifically implicated in causing toxic effect in animals and man [2,3].Mycotoxicosis has been a major but unrecognized food safety issue for several centuries.They are naturally occurring contaminants that causes health related problems when it gets into the body through natural route of ingestion, inhalation or may be absorbed through the skin [4].They are endogenously generated in foods as a result of secondary metabolism [5].These metabolites are synthesized in or on food surfaces and transported through the food chain [6].Mycotoxin production takes place in the mycelium after active fungal growth, but may accumulate in specialized structures such as sclerotia, conidia or in surrounding area [7].Animal studies have shown that, besides acute effects, mycotoxins can cause carcinogenic, mutagenic and teratogenic effects.Mycotoxinscontaminated poultry feed can lead to the transfer of toxins through meat and egg to human beings.
The Food and Agriculture Organization [8] estimating that as much as 25% of the world's Agricultural commodities are contaminated with mycotoxins, leading to significant economic losses.Mycotoxigenic fungi genera include; Aspergillus, Penicillium and Fusarium.The important mycotoxin in the developing countries include aflatoxins, ochratoxins, citrinin, T-2 toxin, deoxynivalenol (DON), fumonisins and zearalenone.

Avian aflatoxicosis 2.1. Aetiology
Avian aflatoxicosis is a disease of poultry caused by aflatoxin.Aflatoxins (AF) are widely distributed toxins produced by Aspergillus.Of the over 180 species of Aspergillus, only a few are aflatoxigenic.After the discovery of AF in the 1960s, A. flavus and A. parasiticus of the section Flavi were the only known AF producers producing the B and B/G types of AF, respectively [10].Other aflatoxigenic species that subsequently emerged are A. nomius (B and G types), A. bombycis (B and G AF), A. ochraceoroseus, and A. pseudotamarii (B type), but they occur less frequently [11,12].A. tamarii, A. parvisclerotigenus (B types), A. rambellii and certain members of Aspergillus subgenus Nidulantes namely: Emericella venezualensis [13] and E. astellata [14] have now been included in the growing list of aflatoxigenic species.A. arachidicola sp.Nov. and A. minisclerotigenes sp.Nov that produce both forms of the toxin, are the latest emerging aflatoxigenic species.The unexpected new comer is A. niger, an ochratoxin (OT) producer which was discovered over four decades ago but was never associated with AF synthesis.However, in a search for aflatoxigenic fungi in Romanian medicinal herbs, [15] showed the capacity of some strains of A. niger to produce AFB1 [16].
AFBI is a member of aflatoxin group is one of the most carcinogenic natural product formed in nature [17].AF has been detected in most countries of the world.Four toxins soon identified: Aflatoxin B1, B2, G1, G2-blue or green florescence under UVlight.•AflatoxinB1mostimportant -highly carcinogenic and widespread occurrence in foods •(B1> M1> G1> B2> M2~ G2).Aflatoxin M1: hydroxylated product of B1appears in milk, urine, and feces as metabolic product

Factor enhancing AF prevalence in feed ingredients and poultry feed
There are several factors enhancing the prevalence of aflatoxigenic fungi and aflatoxin production in developing countries.The factor include the following: The food materials must be infected by aflatoxigenic fungi which deposit the toxins on feed ingredients and concentrated feeds.
The substrate which may be feed ingredients and concentrated feeds posseses a source of energy in the form of carbohydrates and organic and inorganic source of nitrogen, trace elememts and moisture for growth of mould and toxin production [8].
Among cereal, the size and integrity of the seed coat also affects the susceptibility of fungal infection and mycotoxin formation [18] The environmental condition favouring mould growth and AF production are hot and humid conditions, the optimal temperature varies between 24 0 Cand 28 0 C [19] and seed moisture content of at least 17.5% [20].These conditions that favours mould growth are present in most developing countries.
Soil type also affect the level of AF contamination of crops for example, light sandy soil support rapid growth of fungi [21] Presence of other microorganism either bacteria for example presence of Streptococcus lactis and Lactobacillius casei causes reduction in AF production by A. parasiticus [20].Meanwhile fungal metabolites like rubratoxin and cerulenin enhances AF production [16].
Agricultural practices also affect AF contamination of feed ingredient.Off season harvesting and harvesting system that enhances seed breakage would also increase the degree of AF production [22].
A well aerated storage condition used in most developing country to store feed ingredients increases metabolism and subsequent AF production [23].

Occurrence of AF
AF has been found as contaminants in animal feed ingredient worldwide.The occurrence in developing countries is more because there is no strict food and feed quality control programmes to reduce the burden of AF.Also their environmental condition presented as hot and humid climate makes most developing country vulnerable to AF in poultry feed.Among the four AF that are of significance in poultry include; AFB1, B2, G1and G2.AFB1 was detected mostly from animal and feed ingredients from developing countries.Among the feeds ingredients, sorghum, wheat, maize were the most investigated, data on groundnut cake, cotton seed meal and fish meal showed high level of AF contamination.The highest level of AFB1 contamination of feed ingredient were reported in corn from Pakistan 25µg/kg [24], Nigeria wheat was found to be contaminated with 17.10-20.53µg /kg [25].
Higher level of contamination of AF were found in the animal feed than the feed ingredient possibly because of the storage condition which allowed growth and proliferation of mycotoxigenic fungi.In Nigeria AF was detected in poultry feed at 0.0-67.9µg/kg [26], wheat 17.10-20.53µg/kg [25], millet 1370-3475 µg/kg [23].
AF contamination of feed and feed ingredients has been a major concern in many developing country like Pakistan where concentration ranging from 24-37.62 µg/kg were found in poultry feed and poultry feed ingredient [24].
Avian Mycotoxicosis in Developing Countries 97 [16] Table 4. Showing occurrence of AF in animal feed and feed ingredients in developing countries An unacceptably high level of concentration of AF that ranges from 1-1000 µg/kg was found in maize from Uganda [22] About 70% of wheat samples investigated in Algeria were contamination at a range of 0.13-3742mg/kg [33] Table 5. Main clinical signs, performance and pathological features in food producing animals exposed to AF in selected studies.

Pharmacological interaction
Aflatoxicosis has effect on plasma half-life, thus it affects drug effect in the body.[47] observed that chlortetracycline plasma concentrations were lowered due to decreased drug binding to plasma protein [48].Though opinion differed considerably on sparing or aggravating effect caused by the addition of chlortetracycline to feed contaminated with aflatoxin [49,50].

Metabolism and residues
In broilers, metabolites of aflatoxins BI and B2 concentrated in kidney and liver but cleared within 4 days.Then metabolism of Aflatoxin B1 into conjugated aflatoxins B2a and Ml occurred in the liver, which will be metabolized to aflatoxicol [51][52][53][54].Aflatoxin BI was excreted in the bile, urine, and feces as 6 major metabolites [55].The half-life of aflatoxin BI in laying hens is about 67 hours [56], though feed: egg transmission is about 5000:1 [57].Most aflatoxin excreted through the bile and intestine, but aflatoxin BI and aflatoxicol were detected in ova and eggs for 7 days or longer [58][59].Aflatoxin BI accumulated in reproductive organs and its subsequent transmission to eggs and hatched progeny (yolk sac and liver) in poultry [60].It is well established that AFB1 is both carcinogenic and cytotoxic.For example, synthesis of both RNA and DNA was inhibited when AF (5mg/kg of feed) was given to rats over a 6-week-period.The activated AFB1 metabolite (i.e.AFB1-8, 9-epoxide) forms a covalent bond with the N7 of guanine [61] and forms AFB1-N7-guanine adducts in the target cells.The results are G_T transversions, DNA repair, lesions, mutations and subsequently tumor formation [57].The reactive epoxide can also be hydrolyzed to AFB1-8, 9-dihydrodiol which ionizes to form a Schiff's base with primary amine groups in the proteins [58].The short-lived epoxide AFB1 has also been associated with coagulopathy due to reduced synthesis of vitamin K and other clotting factors as a result of sub-lethal intoxication of animals [62].With regard to the cytotoxic effects, AFB1 has been shown to induce lipid peroxidation in rat livers leading to oxidative damage to hepatocytes [63].A more recent study [64], has demonstrated that AFB1 can inhibit cyclic nucleotide phosphodiesterase activity in the brain, liver, heart, and kidney tissues.

Aetiology
This is a disease of bird caused by Ochratoxins.Ochratoxins are among the most toxic mycotoxins to poultry.They are nephrotoxins found in grains and feeds worldwide [65][66].Ochratoxins are isocoumarin compounds linked to L-b-phenylalanine and are designated A, B, C, and D, because of their methyl and ethyl esters.Ochratoxin A (OTA) is the most common and most toxic, and is relatively stable.OTA production is dependent on different factors such as temperature, water activity (aw) and medium composition, which affect the physiology of fungal producers.In cool and temperate regions, OTA is mainly produced by Penicillium verrucosum [67,68] or P. Nordicum [69,70].P. verrucosum mainly contaminates plants such as cereal crops, whereas P. nordicum has been mainly detected in meat products and cheese [69].In tropical and semitropical regions, OTA is mainly produced by Aspergillus ochraceus [71][72][73].A. ochraceus is also referred to as A. allutaceus var allutaceus [71]. A. ochraceus have been reported in a large variety of matters like nuts, dried peanuts, beans, spices green coffee beans and dried fruits, but also in processed meat and smoked and salted fish [71].Two other species of Aspergillus section nigri, A. niger var niger [74][75] and A. carbonarius [76,77] have been reported as OTA producers.The OTA contamination of substrate such as cereals, oilseeds and mixed feeds in warm zones is thought to be due to A.niger var niger in addition to A. ochraceus species [78], whereas A. carbonarius seems to be more common in grapes, raisins and coffee [79][80].
Recently, [81] isolated two new OTA producing Aspergillus species from coffee beans.These species, A. lacticoffeatus and A. sclerotioniger, need further investigations and are provisionally accepted in section Nigri.In addition, another Aspergillus species, A. alliaceus also named Petromyces alliaceus isolated from onions [82] has been previously reported as OTA producer under laboratory conditions [83].This species has been suspected to be responsible for the occasional OTA contamination in Californian figs [84,85] an Argentinean medicinal herbs [67].The biosynthetic pathway for OTA has not yet been completely established.However, labeling experiments using both 14C-and 13C-labelled precursors showed that the phenylalanine moiety originates from the schikimate pathway and the dihydroisocoumarin moiety from the pentaketide pathway.The first step in the synthesis of the isocoumarin polyketide consists in the condensation of one acetate unit (acetyl-CoA) to four malonate units.Recent data showed that this step requires the activity of a polyketide synthase [86].Moreover, the gene encoding polyketide synthase appears to be very different between Penicillium and Aspergillus species [86].In A. ochraceus, the gene of polyketide synthase is expressed only under OTA permissive conditions and only during the early stages of the mycotoxin synthesis [86].No such data are presently available on penicillium.In Penicillium species, ' [86]' observed that P.nordicum and P. verrucosum use two different polyketide synthases for OTA synthesis.This difference is probably related to the P. verrucosum ability to produce citrinin, also a polyketide-based mycotoxin, in addition to OTA.
Source: [91] Table 6.Showing the occurrence of Ochratoxin in developing countries in a selected surveys.
Avian Mycotoxicosis in Developing Countries 101

Occurrence of ochratoxin
OTA was reported by [90] in raw ingredient for making poultry feed were found to be contaminated at range of 00-140 µg/kg in maize 00-98mg/kg in wheat followed by sunflower meal at 00-68 µg/kg.The incidence in India ranges from 16-41% [90].Also high level of contamination was reported in soya meal from Kuwait n-d-40 µg/kg [87].[88] reported a contamination level of 2.56-31.98µg/kg in Venezuela concentrated poultry feed investigated.
Source: [91] Table 7. Showing the main clinical signs, performance and pathological features in poultry exposed to OTA in selected studies

Aetiology
The fumonism, are food borne carcinogenic mycotoxin that affect animals and man.They are evaluated as group 2B component carcinogen [96].It has various analog.Twenty eight fumonisin analogs separated into four main groups, as fumonisin A, B, C, and P series has been identified.The fumonisin B (FB) analogs, comprising toxicologically important FB1, FB2, and FB3, are the most abundant naturally occurring fumonisins, with FB1 predominating and usually being found at the highest levels [96] in feed ingredients and poultry feed in world wide.FB1 accounts for about 80% of the total fumonisins produced inthis substrates, while FB2 usually makes around 20% and FB3 usually makes up from about 5% when cultured on corn or rice or in liquid medium [97][98][99][100].
Different Fusarium species have been reported to produce fumonisins
No doubt the climatic condition to the agricultural practices in these country allow the growth of fungi and subsequent elaboration of toxin in their substrate.

Aetiology
The trichothecenes include deoxynivalenol (DON), 3, monoacetyldeoxynivalenol Different fungi species of the general Fusarium are responsible for the production of this group of mycotoxins.Major producers of trichothecenes are F. graminearum, F. culmorum, F. cerealis, F. poae.

Occurrence of trichothecenes
Occurrence of trichothecenes in feed ingredients and poultry feed in developing countries is as a result of ubiquitous nature of the fungi which are generally found when certain cereal crops like maize, wheat, corn, millet where grown under stressful condition such as drought.These mould occur in soil, hay and especially grains undergoing microbial and possibly enzymatic degradation [20].Direct contamination or indirect contamination of feed may occur.Direct contamination occur when the poultry feed were infected with mycotoxigenic fungi.Indirect contamination may be as a result of fungi elaborating its toxin into the substrate, the incriminating fungi may be removed but the toxin remained in the poultry feed made from such feed ingredients.
Since moulded feed are part of the diet of animal in developing counties, thus all poultry feed are suspect and may contain different level of Trichotheceus toxin.

Diagnosis
Diagnosis is made through observing the appropriate field signs, finding gross as well as microscopic tissue lesions, and detecting the suspected toxin in grains, forages, or the ingesta of affected animals.However, the tests required to detect these toxins are complex and few diagnostic laboratories offer tests for multiple trichothecenes in developing countries.The samples of choice include both refrigerated and frozen carcasses for necropsy examination and a representative sample of the suspected contaminated grain source.Because the toxin is produced under cold conditions, the grain sample should be frozen rather than refrigerated for shipment to the diagnostic laboratory.

Management of avian mycotoxicosis
This involves various practises that reduces fungal contamination of feedstuff and possible use of mycotoxin binders in feed.The clinical signs seen in avian mycotoxicosis are not pathognomonic so the presence of toxin in feed with the associated clinical signs may help clinician to make effective diagnosis and withdrawal of contaminated feed can help to ameliorated the disease condition.Preventive and control of mould in feed is key to achieving control of avian mycotoxicosis.
Following good agricultural practices during both pre-harvest and post-harvest conditions would, minimize the problem of contamination by mycotoxins such as aflatoxins, ochratoxin and trichothecene mycotoxins.These include appropriate drying techniques, maintaining proper storage facilities and taking care not to expose grains.

Dry the feed ingredients
Fungi cannot grow or mycotoxins be produced in properly dried foods, so efficient drying of commodities and maintenance of the dry state is an effective control measure against fungal growth and mycotoxin production.
To reduce or prevent production of most mycotoxins, drying should take place as soon after harvest and as rapidly as feasible.The critical water content for safe storage corresponds to a water activity (aw) of about 0.7.Maintenance of feeds below 0.7 aw is an effective technique used throughout the world for controlling fungal spoilage and mycotoxin production in foods.
Problems in maintaining an adequately low aw often occur in the tropics, where high ambient humidity make control of commodity moisture difficult.Where grain is held in bags, systems that employ careful drying and subsequent storage in moisture-proof plastic sheeting may overcome this problem.
While it is possible to control fungal growth in stored commodities by controlled atmospheres or use of preservatives or natural inhibitors, such techniques are almost always more expensive than effective drying, and are thus rarely feasible in developing countries.

Avoid grain damage
Damaged grain is more prone to fungal invasion and therefore mycotoxin contamination.It is thus important to avoid damage before and during drying, and in storage.Drying of maize on the cob, before shelling, is a very good practice.
Insects are a major cause of damage.Field insect pests and some storage species damage grain on the head and promote fungal growth in the moist environment of the ripening grain.In storage, many insect species attack grain, and the moisture that can accumulate from their activities provides ideal conditions for the fungi.To avoid moisture and mould problems, it is essential that numbers of insects in stored grain be kept to a minimum.Such problems are compounded if the grain lacks adequate ventilation, particularly if metal containers are used.

Ensure proper storage conditions
While keeping commodities dry during storage in tropical areas can be difficult, the importance of dry storage cannot be overemphasized.On a small scale, polyethylene bags are effective; on a large scale, safe storage requires well-designed structures with floors and walls impermeable to moisture.Maintenance of the water activity of the stored commodity below 0.7 is crucial.
In tropical areas, outdoor humidities usually fall well below 70% on sunny days.Appropriately timed ventilation, fan-forced if necessary, will greatly assist the maintenance of the commodity at below 0.7 aw.Ideally, all large-scale storage areas should be equipped with instruments for measuring humidity, so that air appropriate for ventilation can be selected.
Sealed storage under modified atmospheres for insect control is also very effective for controlling fungal growth, provided the grain is adequately dried before storage, and provided diurnal temperature fluctuations within the storage are minimised.
If commodities must be stored before adequate drying this should be for only short periods of no more than, say, three days.Use of sealed storage or modified atmospheres will prolong this safe period, but such procedures are relatively expensive and gaslight conditions are essential.
A proven system of storage management is needed, with mycotoxin considerations an integral part of it.A range of decision-support systems is becoming available covering the varying levels of sophistication and scale involved.

Control
Control of mycotoxin in poultry feed is important and it should be hinged on eliminating mycotoxin from the food chain.Mycotoxygenic fungi are naturally found in soil and air, which makes it difficult to prevent their contamination of agriculture commodities.Nevertheless attempts should be made to control factors that affects the growth of mycotoxigenic fungi and the subsequent toxin production.Factors which include warm temperature between (20 o c to 30 o c), high moisture content (20-25%), water activity (aw) of about 0.7aw and relative humidity of 70% and above.These factors enhance fungi growth and mycotoxin production (143,145).
Before harvesting of crops damage to grains as a result of field insect pest and some storage species damage grains and promote fungal growth in the environment of ripening grain.Strategies used in various preventive measure in poultry feed involves good agronomic practices, detoxification of mycotoxin in grains use of mould inhibitors, genetic approach through improved breeds of plants.

Physical decontamination
Decontamination of mycotoxin from cereal crops used in the production of poultry feed can be classified as physical decontamination, biological decontamination and chemical decontamination [146].[145] suggest the following method of elimination of mycotoxin in grains which include, Density segregation and floatation, cleaning and washing, seiving, dehulling, hand picking, irradiation, milling, thermal degeneration.[147] observed that washing using distill water resulted in 65%-95% reduction of DON (16-24mg/kg) and 2% to 61% of ZEN (0.9-1.6mg/kg) in contaminated barley and corn.
Density segregation in certain liquid or fractionation by specific gravity help to segregate fungi infected and mycotoxin contamination grains used in the production of poultry feed.[148].It was also observed that fumonisms present in broken corn kernels is about 10 fold higher than that in intact corn therefore the separation based on the size has been suggested.[147,146] Irradiation is also a useful tool in inactivation of some mycotoxin reported ultrasonication been used in contaminated corn without affecting the grain composition.Several workers reported the use of Gamma irradiation to reduce Zearelenone DON and T-2 toxin in corn, wheat.[148][149][150]

Biological decontamination
This involved systemic degradation of toxins leading to a less toxin product.[151] reports a fungus yeast Expoliata spinnifera was able to grow on fumonisin B1as a sole of carbon source.The hydrolysis of fumonisin B1 yields free Tricarboxylic acid and aminopental, the intermediate aminopentol undergo oxidative deamination.Sacchromyces cerevisiae ferment zearalenone converting it into beta-zearelenol, which has less activity compared to the parent compound.[152] Feed additive like mycotoxin inactivates trichothecenes by enzymatic decontamination of the 12-13 epoxy ring, and zealenone by the enzymatic opening of the lactone ring [148][149][150][151][152]

Detoxification of mycotoxin feed
Moist ozone and dry ozone were able to reduce DON concentration in contaminated corn up to 90% and 70% respectively [153].[154] reports 79% reduction in fumonism level in corn.

Table 1 .
Development of poultry meat production in developed and developing countries (million tonnes).

Table 2 .
Development of poultry hen egg production in developed and developing countries (million tonnes)

Table 3 .
Showing fungi genera and the associated mycotoxin.

Table 8 .
Occurrence of FB1 In Feed Ingredient In Developing Countries

Table 9 .
Showing the main clinical signs, performance and pathological features in poultry exposed to fumonism in selected studies

Table 10 .
Occurrence of Trichothecenes in Feed Ingredients In Developing Countries

Table 11 .
Showing the main clinical signs, gross and histopathological changes in some poultry species.