RESUMEN
Most parts of Eritrea are classified as arid and semi-arid land (ASALs) which are characterised by dryness, high ambient temperatures and low precipitation. The country has three different environmental landscapes: highland, Western lowland and Eastern lowland agro-ecological zones (AEZs). The geophysical and biophysical characteristics of the AEZs vary. Indigenous cattle which are mainly kept in extensive production system have to cope with the adverse climatic conditions of these AEZs. They have to adapt to the harsh climate, poor feed quality and endemic diseases and parasites and reproduction challenges in the AEZs. The underlying genetic basis of the indigenous cattle adaption to the specific AEZs in Eritrea is limited. In this study, it is hypothesized that the indigenous cattle have evolved and developed unique adaptive characteristics because of being reared in specific ecological landscapes. This was tested using the landscape genomics and analysis of selection signatures to ascertain the genetic basis of their adaptability to the nutritional and environmental constraints that characterise the AEZ conditions. The study was carried out in three different environmental landscapes: highland, Eastern lowland and Western lowland AEZs. Blood samples were collected from a total of 188 indigenous cattle populations sampled from the three AEZs. DNA was extracted and genotyped using the genotype by sequencing (GBS) method. Analysis revealed the existence of medium to high genetic diversity between and within the indigenous cattle populations. Scanning of selection signatures revealed genomic regions under positive selection. The regions harboured genes (IFNAR2, CASR, AHSG, ATP1B3, AIRE, ROBO2, SCHIP1 and PARS2) of importance for facial morphology, locomotion, mineral homeostasis, immune system and skeletal and muscle system development. Findings pointed out the influence of AEZ landscapes on the genetic differentiation of indigenous cattle appearances probably due to selection driven by diverse climatic and biophysical conditions. The differentiation is orientated towards adaptive characteristics.
Asunto(s)
Adaptación Fisiológica , Genómica , Adaptación Fisiológica/genética , Animales , Bovinos/genética , Eritrea , Genoma , Genotipo , Polimorfismo de Nucleótido Simple , Selección GenéticaRESUMEN
BACKGROUND AND METHODS: A retrospective study of the national health profile of Eritreans, focusing on acute respiratory tract infection (ARTI), tuberculosis (TB), diarrhoea, sexually transmitted diseases (STDs) and HIV/AIDS, was done on data from 1998 to 2003 through a health information management system. Records were included for patients of all ages receiving outpatient and inpatient hospital services during the study period. All incidence rates were given as cases per 100,000 population. RESULTS: The incidence of ARTI increased from 6,500 cases per annum in 1998 to 8 500 in 2003, representing a 30% increase. Diarrhoea rates remained unchanged, averaging 3,000 cases. For both ARTI and diarrhoea, rates were at least 3 times higher in children under 5 years of age than in those over 5 years of age. The incidences of TB and STDs decreased from 370 and 220 in 1998 to 170 and 80 in 2003, respectively. HIV/AIDS incidence increased from 40 in 1998 to 65 in 2003, reflecting a 60% increase. The case fatality rates (CFRs) for HIV/AIDS and TB were 12% and 2% in 1998, increasing to 14% and 3%, respectively, in 2001. The CFR for ARTI and diarrhea remained low at 0.3%. CFRs were higher in children under 5 years than in those over 5 years for all the diseases but rates declined consistently, probably reflecting the positive impact of the introduction of the integrated management of childhood illness (IMCI). Although the incidence rate of HIV/AIDS was relatively low compared with rates for TB, ARTI and diarrhoea, the HIV/AIDS CFR was relatively high, posing a threat to the gains made in control of infectious diseases. The disease burden from TB and STDs declined over the 6-year study period, while that from ARTI and HIV/AIDS increased. Consequently the overall disease burden from communicable diseases remained unchanged over the study period.