Isolation, Characterization and Pathologic Studies of Aflatoxin and Aspergillus Species from Local Cashew Nuts Consumed In Enugu State, Nigeria

Abstract

In a study conducted to investigate the isolation, characterization, pathologic studies of aflatoxin and Aspergillus species from local cashew nuts, a total of 152 samples of exposed and unexposed roasted cashew nuts were analyzed between May and December 2015. A total of six genera of fungal isolates consisting of Aspergillus species 178(76.0%), Mucor species 23(9.8%), Rhizopus species 17(7.3%), Rhodotorula species 11(4.7%), Candida species 4(1.7%), and Geotrichum species 1(.04%) being the least were isolated. Out of the 62 samples of exposed cashew nuts group, Aspergillus niger showed the highest incidence 32(37.2%) followed by Aspergillus flavus 22(25.5%), Mucor species 12(13.9%), Aspergillus fumigatus 8(9.3%), Rhizopus species 7(8.1%), Rhodotorula species 3(3.4%), Aspergillus nidulans 1(1.1%) and Candida species 1(1.1%). Geotrichum species was not isolated from this group. Of the 90 samples of cashew nuts under the unexposed category, Aspergillus flavus ranked highest 61(41.2%) followed by Aspergillus niger 49(33.1%), Mucor species 11(7.4%), Rhizopus species 10(6.7%), Rhodotorula species 8(5.4%), Aspergillus fumigatus 4(2.7%), Candida species 3(2.0%), Aspergillus nidulans 1(0.6%) and Geotrichum species 1(0.6%). The total fungal isolates from unexposed cashew nuts (148) were greater in number than the fungal isolates from the exposed group (86) whose difference was not statistically different (P>0.05). Out of 62 samples exposed cashew nuts investigated, Aspergillus flavus yielded mixed growth with other fungal isolates. Aspergillus niger + Aspergillus flavus 9 (64.2%) showed the highest incidence while Aspergillus flavus + Aspergillus fumigatus 1(14.2%) showed the least growth. Of the 90 samples of unexposed cashew nuts investigated, Aspergillus flavus + Aspergillus niger 29(63%) showed the highest incidence while Aspergillus flavus + Aspergillus nidulans 1(2.1%) and Aspergillus flavus + Aspergillus fumigatus 1 (2.1%) showed the least incidence. However there was a significant difference observed between the mixed growth of Aspergillus flavus + Aspergillus nidulans and Aspergillus flavus + Geotricum species (P < 0.05). Of the 234 fungal isolates encountered in the study, 83(35.4%) of Aspergillus flavus were isolated. Similarly, there was a significant difference between the number of Aspergillus flavus and non- Aspergillus flavus isolated. (P< 0.05). Out of the 83(35.4%) of the Aspergillus flavus-contaminated cashew nuts examined, 17(65.3%) yielded positive aflatoxin detection (P> 0.05). In the study conducted to investigate the pathological effects of the consumption of contaminated cashew nut using wistar rats fed with a 50% aflatoxin contaminated cashew nut diet, the liver and renal function test results showed no statistically significant difference (P>0.05) when the test and control animals were compared, though the calcium Ca2+ and creatinine levels showed a statistically significant difference (P<0.05). The histological results however revealed some widening of the sinusoids, central canal rupture, degenerating hepatocytes and inflammatory cellular infiltration especially within the sinusoids suggesting cirrhosis for the test animals while the kidney shows normal features. The result of the study suggests that the consumption of contaminated cashew nuts which is a major snack food widely patronized in Enugu may pose a serious public health hazard that may target the liver aside other minor issues. This therefore emphasizes the pertinent need for cashew nut protection studies and implementation in line with the recommendation of the FAO (Food and Agriculture Organization) and WHO (World Health Organization).