There is a scarcity of information concerning prevalence of poultry aspergillosis and other fungal diseases in Zaria and Kaduna areas of Kaduna State, Nigeria. This study was conducted to determine the prevalence of Aspergillus species and other fungi in sick poultry presented to the avian clinic of Veterinary Teaching Hospital of the Faculty of Veterinary Medicine, Ahmadu Bello University Zaria. Data on clinically suspected reported cases of aspergillosis and their corresponding Microbiology results between 1980 and 2008 were reviewed, assembled and summarized. Analysis of the 132 cases of sick birds suspected of aspergillosis revealed 114 (86.4%) Aspergillus and other fungi. Eleven different fungi species ascribed to 9 genera were isolated, Aspergillus spp (45.5%), Candida spp (14.4%), Mucor spp (10.6%), Rhizopus spp (10.6%), Penicillium spp (1.5%) and sterile hyphae (1.5%), Alternaria spp, Absidia spp, and Geotrichum spp each with a prevalence of 0.75%. The month of July and November recorded the highest percentage of disease and fungal isolates. There was also no significant difference (p> 0.05) between the monthly fungal isolation and the corresponding average humidity and rainfall. This study showed that aspergillosis is prevalent in Zaria and Kaduna areas and that the disease occurs throughout the year. Good management practices that include; reduction of stressors, overcrowding and provision of adequate ventilation reduces moldy growth in poultry environment and are recommended for the farmer(s).
The most common fungal infection in birds appears to be Aspergillosis and Candidiasis (Orosz, 2000). Aspergillosis has been reported in poultry in Zaria area and in Nigeria at large (Salami et al., 1987; Abdu et al. 1995; Saidu et al. 1999a) as well as the world over (Sajid et al. 2006; Saleh et al. 2010). All species of the genus Aspergillus (A. fumigatus, A. flavus, A. niger, A. nidulans and A. terreus) are known to cause aspergillosis with A. fumigatus being the most commonly encountered and most pathogenic Aspergillus species in poultry (Greenacre et al. 1992; Abdu et al. 1995; Joseph, 2000, Jones and Orosz, 2000, Deem, 2003). Aspergillus fumigatus is a ubiquitous and saprophytic fungal that is capable of causing severe and life threatening illness in birds, mammals and immunocompromised humans (Jones and Orosz, 2000; Joseph, 2000; Rambach et al., 2005; Khosravi et al., 2009). The disease may appear as an acute or chronic disease characterized by high and low mortality respectively (Orosz, 2000; Tell, 2005; Islam et al. 2009). Aspergillosis has been reported in association with viral infections such as infectious bursal disease and isolated in tissues of birds that died of avian influenza (Okoye et al., 1991; Dashe, 2007). Other fungi found in poultry in Zaria were Mucor spp in a suspected case of Newcastle disease and mucormycosis in a flock of seven week old ostrich (Saidu et al., 1999a, 1999b). It is in the light of the above reports that a retrospective study was carried out to determine the prevalence of aspergillosis from all the reported cases brought to the poultry clinic of the Veterinary Teaching Hospital, Zaria. This study will also reveal the extent of the problem of aspergillosis, the fungi responsible in the area as well as any correlation between the disease and the two seasons of the area.
Materials and Methods
Source of Data and Collation
Clinical and laboratory records over a period of twenty eight (28) years (1980-2008) from the Microbiology unit of the Department of Veterinary Pathology and Microbiology and the Avian Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria, were reviewed, summarized and analyzed. The records included information on age, sex and flock size of the chickens, necropsy diagnosis and registration number (for identification), sample sent for laboratory isolation and identification of possible fungi responsible for the disease symptoms. The temperature, humidity, and rainfall over the same period were collected from the meteorological unit of the Institute of Agricultural Research, Ahmadu Bello University Zaria for comparative analyses of these parameters to the frequency of isolation of the causative fungi.
The data obtained were reduced and presented in tables and charts. Isolation rate of fungi from lung/crop samples of dead chicken suspected to be cases of aspergillosis were analyzed using Chi-Square and simple regression comparing prevalence of aspergillosis with humidity and rainfall for Zaria.
Out of the 132 cases suspected of avian aspergillosis, 114 (86.4%) were confirmed based on laboratory isolation. Eleven different fungi species ascribed to 9 genera were isolated, Aspergillus spp (45.5%) Candida spp (14.4%), Mucor spp (10.6%), Rhizopus spp (10.6%), Penicillium spp (1.5%) and sterile hyphae (1.5%), Alternaria spp, Absidia spp, and Geotrichum spp each with a prevalence of (0.75%).
Aspergillus spp was the most (45.5%) commonly isolated fungi throughout the period of study (Table 1 and 2) with A. fumigatus, A. niger and A. terrus making up 55 (91.70%), 4 (6.70%) and 1 (1.70%) respectively of the total Aspergillus spp isolates. Aspergillus spp was also the most commonly isolated fungi during the rainy season and dry seasons; 30 (54.5%) and 25 (45.5%) respectively, followed by Candida, Rhizopus and Mucor. There was also no significant difference in fungal isolation/cases between the rainy and dry seasons.
The highest percentage of fungal isolation occurred in the months of July (14.9%) and November (14.9%). The average humidity and rainfall in the months of May-October (rainy season) was greater than that in the months of November- April (dry season). There was no significant difference (p> 0.05) in fungal cases/isolation when the humidity/rainfall was higher or lower. There was also no significant difference (p> 0.05) between the monthly fungal isolation and the corresponding average humidity (Table 3)
Table 1: Fungi isolated from suspected cases of aspergillosis between 1980 and 2008 in the Microbiology Laboratory of the Department of Veterinary Microbiology, Ahmadu Bello University Zaria.
|S/no||Fungi spp isolated||Number of fungi isolated||% Isolated|
Table 2: Mean seasonal prevalence of fungi isolated from sick birds in the Microbiology unit of Department of Veterinary Microbiology between 1980 and 2008.
|Fungi isolated|| May- October
| November- April
p > 0.05
Table 3: Mean monthly distribution of fungi isolated in the Microbiology Laboratory of the Department of Veterinary Microbiology as in relation to the average humidity and rainfall between 1980 and 2008.
|% of Fungi isolated|
p > 0.05
Environmental conditions promote the growth and spread of fungi while intensive animal husbandry characterized by overcrowding promotes and sustains fungal outbreaks (Joseph, 2000; Kapentanov et al. 2011). The result of the retrospective analysis showed that there was no significant difference in the occurrence of aspergillosis during the rainy and dry seasons i.e. there was an all year round prevalence of the disease. This may be explained by the fact that spores are produced in abundance during the wet and humid season of the year making them available in the environment even during the dry season. Although the general environment may be dry and less humid during the dry season, the inside of a poultry pen may become humid enough to allow for germination of the Aspergillus spores which when inhaled in large numbers by the chickens may result in the disease. There was a higher prevalence of fungal isolation in the months of July and November. This periods coincide with the peak of the rainy season (July) and the harmattan (November) which are characterized by high humidity (which supports the germination of the fungal spores) and windy conditions (which supports the dispersal of the fungal spores) respectively. The nature of the avian respiratory system makes colonization by fungi easy. It is characterized by large spaces (airsacs) where air becomes humidified at body temperatures approaching 40o C in addition to an absence of rapid immune response due to the avascular nature of these structures. This allows the establishment of fungal growth when the birds are exposed to high spore concentrations (Verwoerd, 2002), though even low level spore load inhaled can result in infection in highly stressed or very sensitive individual birds. In addition to the above factors the sensitivity of birds to gliotoxin, which causes tissue necrosis and provide a nutrient rich environment has been reported to aid in survival of Aspergillus in tissues (Tell, 2005). Also, the indiscriminate use of antibiotics by poultry farmers may predispose the birds to infection due to destruction of antagonizing bacteria flora.
Aspergillus fumigatus was the most common fungal isolated from the birds in this study. This is in agreement with the findings of other workers (Greenacre et al., 1992; Abdu et al. 1995; Joseph, 2000, Jones and Orosz, 2000; Deem, 2003; Burco et al. 2012) who identified A. fumigatus as the major cause of avian aspergillosis. This may be because the spores of A. fumigatus are smaller than the spores of other Aspergillus species (Richard and Thurston, 1983).
Though, some pathogenic molds such as Mucor, Rhizopus, Geotricum or even Penicillium and other Phycomycetes were encountered in the study, their ability to produce disease in birds is yet to be ascertained. It is obvious from this retrospective study that other fungi were isolated in association with A. fumigatus or alone as the sole organism found in clinical cases of aspergillosis. Such organisms isolated alone were A. niger, Rhizopus, Mucor and Candida. The roles of these organisms especially in the pathology of mycosis is yet to be fully understood but their pathogenicity is not in doubt either in poultry or other species of animals and man (Ainstworth and Austwick, 1973; Sa’idu et al., 1999b). Another Aspergillus spp that has received little attention but has been isolated in avian aspergillosis in this study is A. terreus. Although A. terreus is not well known as a sole cause of aspergillosis in poultry, it is nevertheless a pathogen of birds (Redig, 1980) and was isolated from tracheal swabs of diseased chickens in this work. Other Phycomycetes such as Alternaria and Absidia were isolated in association with A. fumigatus. Geotrichum spp which was also isolated is a member of normal flora of birds but it has been implicated in bovine mycotic abortion (Ainswick and Austwick, 1973). Isolations of Phycomycetes from avian aspergillosis either alone or in association with A. fumigatus should not be discarded as unimportant, but they should be studied for a better understanding of their status in fungal diseases of poultry because each of them isolated in this study have been known to cause disease either alone or in combination with other organisms (Ainstworth and Austwick, 1973; Sa’idu et al., 1999b).
The result showed that numerically, there was a higher number of aspergillosis reported in the months of July and November during the years studied and that the disease occurred throughout the year (rainy and dry seasons). Some of these fungi have the potential to produce toxins which are also lethal to the birds thus causing toxicosis. The isolation of these fungi is also of public health significance as they are known to cause diseases (when the spores are inhaled) especially in immunocompromised individuals. They therefore also pose a potential threat to poultry house workers.
It is recommended that farmers be advised to maintain hygienic environment throughout the year but in particular during the months of July and November. Farmers should also provide good ventilation in the poultry houses, reduce stress on the birds and overcrowding as this provides good environment for fungi proliferation and spread. Poultry workers and farmers should be advised on the need to use protective gears especially face mask when working in poultry houses or with poultry.
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