Journal of Morphology and Anatomy

The post hatch (PH) development of the thymus gland in turkey (Meleagris gallopavo) was studied from day (D) 1 post hatch to day 140. The thymus gland composed a bilateral chain of 5-8 irregular elliptical lobes that varied in size from cranial to caudal lobes, and from pale red to pink in color. Histologically, in all ages the thymus was enclosed by a connective tissue capsule from which septa penetrated and divided the stroma into incomplete lobules. Each lobe consisted of a central medulla surrounded by a lobulated cortex. At D 1 PH, lymphocytes and few granulocytes dominated the parenchyma with classical Hassall’s corpuscle in the medulla. By D 14, reticular structures were observed in the medulla, and many vacuoles were associated with it by D 28. At D 42, several pink cells and highly basophilic cells dominated the medulla. From D 56, strands of connective tissue fibers formed network in the parenchyma. Encapsulated nodules dominate by lymphocytes with some plasma cells were observed at D 112. At D 140, there was marked depletion of thymic cells, and the distinction of the cortex from the medulla was in apparent.

In Ethiopia the majority of small holder farmers are practicing subsistence farming on less than a hectare of land. But the largest component of the farmers is growing and producing of maize on the subsistence farm. It accounts 55.6% yield production among cereals. But currently newly emerging viral diseases is limiting its production in Ethiopia since introduced in the year 2013/2014 cropping season in the Upper Awash Valley areas. This disease was latter recognized as Maize Lethal Necrosis Disease (MLND) to cause various levels of damage ranging from low infection rate to total crop failure. The exact time of MLND occurrence in Ethiopia is not determined but its presence was confirmed in 2014. Subsequent assessments and reports indicated that the disease is widely distributed in major maize producing areas of Ethiopia; namely, Amhara, Benishangul-Gumuz (BSG), Oromia, Southern Nation, Nationality and Peoples (SNNP) and Tigray regions. It seriously affected yields and the infected plants regularly remain barren, small or deformed ears and no seed at all. Vectors and infected soil and seed are responsible agents for the spread of MLND. Since MLN is strange for the country there is no integrated management strategies developed for the management of MLN. However, some of the management options available from world experience showed that significant loss of the crop can be reduced using management options integrally. As the maize genotypes reaction is base for breeders, Ethiopian and some Kenya maize germ plasmas against the disease are on trial in Ethiopia. Capacity building of scientists and regulatory agencies should be emphasized to diagnose MLND causing viruses and formation of new hybrids and breeding populations from resistant sources should be future prospect.