NAHDIC has been engaged in research activities over the last 20 years and has contributed more than 350 published articles to the scientific community.  Research activities at NAHDIC focus on problem solving and generating information and data to support disease control and prevention measures.  Research initiatives are conducted with NAHDIC technical partners found both within the country and abroad. This includes collaborations with university students. An average of 30 undergraduate and post-graduate (MSc and PhD) Ethiopian university students conduct their research at NAHDIC per year. Currently, there are about 24 active ongoing research projects. Some of the topics are done on bovine tuberculosis, PPR, CBBP, FMD, BVD, IBR, brucellosis and infectious bronchitis. 

 

Study on Poultry Coccidiosis in Tiyo District, Arsi Zone, Ethiopia

Getachew Gari1, Getachew Tilahun2and Ph. Dorchies3

1National Animal Health Research Center, P.O. Box: 4, Sebeta, Ethiopia,

2Aklilu Lemma Institute of Pathobiology, Addis Ababa University,

 

3Ecole National Veterinary, Toulouse, France

 

Abstract

The objective of this study was to investigate the prevalence of poultry coccidiosis and identify coccidial species occurring in the study area on local strain and Rhode Island Red breed chicken. The study involved questionnaire survey, fecal examination, necropsy examination and identification of coccidial species based on their morphology, predilection site in the intestine and sporulation time. More than 75% respondents indicated that poultry production and income generated from poultry production in the rural community is the major income source for females and youth and bloody diarrhea predominantly appeared during wet season than chalky, yellow or green diarrhea. Public and private veterinary service centers have no anti coccidial drugs and other medicaments used for poultry diseases. Frequency detection of oocyst in the fecal samples from Rhode Island Red breed and local strain chicken was 80.65% and 61.25% respectively. This finding indicated that coccidial infection in Rhode Island Red breed was significantly higher than in local strain chicken (p < 0.05). The lesion score and mean oocyst output per gram feces was also considerably higher in Rhode Island Red breed than in local strain chicken (p < 0.05, p <0.001 respectively), which may be the difference due to management system and breed. Clinical coccidiosis occurrence in Rhode Island Red breed and local strain chicken was 22.58% and 12.25% respectively. There was no statistically significant difference in clinical coccidiosis occurrence between the two genotype chickens and system.  Eimeria species identified in descending order of their occurrence were E. tenella, E. acervulina, E. necatrix, E. maxima and E. mitis. Mixed infections were the predominant in both production systems. E. mitis was diagnosed for the first time in Ethiopia.

 

Key words: Coccidia, Eimeria, infection, Local strain chicken, prevalence and Rhode Island Red breed

Detection of Multiple Drug-Resistant Trypanosoma congolense Populations in the Five Hotspot Village Cattle of Gurage Zone, Abeshegedistrict, South west Ethiopia

Tekle, T.1, Getachew, T.2, Hagos, A. 3, Cherenet, T.4,Getachew G.5, Van Den Abbeele, J.6, Clausen P-H.7, Hoppenheit,A.8, Mattioli R.C.7,Peter R.8, Delespaux,V.9

 Abstract

Background:  African animal trypanosomosis causes with direct and indirect annual losses that run into billions of dollars. The disease is assumed to cause hunger and poverty in most sub-Saharan African countries since it represents aserious impediment to sustainable livestock production. A longitudinal study was carried out from November to December 2013 to evaluate the susceptibility of trypanosomes totrypanocidal drug treatment in village cattle populations in Abeshege district.Five hot-spot villages that scores prevalence rate of 10% and above during cross-sectional studies were purposively selected and participated in the study. Eighty positive cattle in the study villages were examined for trypanosomes. All trypanosome-positive cattle were randomly allocated into twotreatment groups: a group treated with 0.5mg/kg/bw. isometamidium chloride (ISMM) and a group treated with3.5 mg/kg bw. diminazeneaceturate (DIM). The cattle were monitored for trypanosomes at day 14 and 28post-treatment.Out of the total of 40 animals treated with 1mg/kg bw. ISMM 11 (27.5%) became parasitaemic and 29 (72.5)  cattle wereaparasitaemic 14 days post-treatment and cattle treated withdiminazeneaceturate  3.5 mg/kg/bw. 19 (47.5%) found to be parasitaemic cattle and 21 (52.5%) were aparasitaemic 14 days post-treatment with a cumulative failure of (37.5%) 30/80. Out of the total of 11 animals that were positive for the treatment of  0.5 mg/kg/bw ISMM and treated with diminazene 6 (54.5%) found to be positive and 5 (45.5%) were aparasitaemic on day 28 post-treatment and 19 cattle that were found positive for the treatment of 3.5 mg/kg/bw. Diminazeneaceturate were treated with 0.5 mg/kg/bw. ISMM 5 (26.3%) found to be positive and 14 (73.7%) were aparasitamic on day 28 post treatment with a cumulative failure of (36.6%) 11/30. The use and overreliance on trypanocides in the control of trypanosomosis will ultimately lead to multiple drug-resistant trypanosome populations as detected in villages in south-west Ethiopia making the use of drugs doubtful. Effective alternative methods for trypanosomosis control ought to substitute chemotherapy to ensure sustainable cattle production in these villages. Since there is no single strategy for containing trypanocidal drugresistance, promotion of an integrated approach combining proven trypanosomosis control approaches in high trypanosomosis risk areas is most desirous. The best-bet strategy this study recommended for areas with multiple drug resistance included area-wide community tsetse control, control of co-infections to exploit self-cure against resistant trypanosome populations and the rational use of trypanocidal drugs which should be urgently promoted at all levels as a way of containing or reversing resistance.

Keywords: Cattle, Ethiopia, Trypanosomosis risk, T.congolense, Trypanocide resistance

Aberrant Use and Poor Quality of Trypanocides: a Risk for Drug Resistance in South western Ethiopia

T.Tekle1, G. Terefe3*, T. Cherenet2, H. Ashenafi3,
K. G. Akoda4, A. Teko-Agbo4, J. Van Den Abbeele5,
G. Gari1, P.-H. Clausen6, A. Hoppenheit6, R.
C. Mattioli7, R. Peter8, T. Marcotty9, G.
Cecchi10 and V. Delespaux11

 Abstract

Trypanocidal drugs have been used to control African animal trypanosomosis for several decades. In Ethiopia, these drugs are available from both authorized (legal) and unauthorized (illegal) sources but documentation on utilization practices and quality of circulating products is scanty. This study looked at the practices of trypanocidal drug utilization by farmers and the integrity of active ingredient in trypanocides sold in Gurage zone, south western Ethiopia. The surveys were based on a structured questionnaire and drug quality determination of commonly used brands originating from European and Asian companies and sold at both authorized and unauthorized markets. One hundred farmers were interviewed and 50 drug samples were collected in 2013 (Diminazene aceturate=33 and Isometamidium chloride=17; 25 from authorized and 25 from unauthorized sources). Samples were tested at the OIE-certified Veterinary Drug Control Laboratory (LACOMEV) in Dakar, Senegal, by using galenic standards and high performance liquid chromatography. Trypanosomosis was found to be a major threat according to all interviewed livestock keepers in the study area. Diminazene aceturate and isometamidium chloride were preferred by 79% and 21% of the respondents respectively, and 85% of them indicated that an animal receives more than six treatments per year. About 60% of these treatments were reported to be administered by untrained farmers. Trypanocidal drug sources included both unauthorized outlets (56%) and authorized government and private sources (44%). A wide availability and usage of substandard quality drugs was revealed. Twenty eight percent of trypanocidal drugs tested failed to comply with quality requirements. There was no significant difference in the frequency of non-compliance between diminazene-based and isometamidium chloride products (P=0.87) irrespective of the marketing channel (official and unofficial). However, higher rates of non-compliant trypanocides were detected for drugs originating from Asia than from Europe (P=0.029). Conclusion: The findings revealed the presence of risk factors for the development of drug resistance, i.e. wide distribution of poor quality drugs as well as substandard administration practices. Therefore, it is strongly recommended to enforce regulatory measures for quality control of veterinary drugs, to expand and strengthen veterinary services and to undertake trypanocidal drug efficacy studies of wider coverage.

Keywords: Diminazene, Isometamidium, Trypanocide, Drug quality assessment, Drug utilization practice, Ethiopia

Sero-prevalence of Newcastle Disease in Backyard Chickens in Sebata Hawas District, Central Ethiopia

 

Tilahun Sori1, Amare Eshetu1, Asamanew Tesfaye2

AbebeGaroma2 and Shimelis Mengistu1

 

 

1College of Veterinary Medicine, Haramaya University, P.O. Box: 138, Dire Dawa, Ethiopia,

 

 2National Animal Health Diagnostic and Investigation Center, Sebata, Ethiopia

 

 

Abstract

The study was conducted in Sebata Hawas District, Oromia Region, Central Ethiopia with the objective of determining the sero-prevalence of Newcastle disease (ND) in backyard chickens using blocking-enzyme linked immunosorbent assay from November, 2014 to March, 2015. A total 344 chicken sera were collected from five randomly selected peasant associations (PA) for this study. An overall sero-prevalence of 11.34% (95% CI: 8.19-15.17%) of the Newcastle disease was recorded in the study area. The highest sero-prevalence 20% (95% CI: 12.83-28.93) was recorded at Dima peasant association which is located near to market and the sero-prevalence in each PA ranges from 0% to 20%. The sero-prevalence of Newcastle disease significantly varied among peasant associations (χ2 = 21.0; P=0.00). The sero- prevalence of Newcastle disease in cross and local breeds of chickens were 13.9% and 10.7% respectively and the difference was not significantly varied between breeds of chickens =0.59; P=0.44). Similarly, no significant difference in sero prevalence was observed between female and male; young and adult chickens.

Key words: Poultry, Traditional, Peasant Association, Newcastle Disease Sero-Prevalence

Sero-prevalence Study on Infectious Bursal Disease and Associated Risk Factors in Backyard Chicken Production in Sebeta Hawas District, Oromia, Ethiopia

Asamenew Tesfaye1, Beshada Tesfaye2 and Moti Yohannes2

  

1National Animal Health Diagnostic and Investigation Center, P.O. box 04, Sebeta, Ethiopia,

 

2Jimma University, Collage of Agriculture and Veterinary Medicine

  

Abstract

A cross sectional study was conducted in Sebeta Hawas district from November 2014 to march 2015 to determine the sero-prevalence of infectious bursal disease (IBDV) using Indirect ELISA techniques and associated risk factors. A total of 180 chickens raised in the backyard production system were bleed to get sera from randomly selected five PA’s in the district. An overall seroprevalence of 38.3% (69/180) for the entire study area were detected. The highest (58.6%) and lowest (9.4 %) seroprevalence was recorded in Koche and Tefki PA’s respectively. The difference was statistically significant (p-value < 0.05) among study areas. In relation to age highest seroprevalence of IBD was recorded in 3-12 weeks age 45.8% (11/24) and lowest seroprevalence was recorded in chickens 13-24 weeks and greater than 24 weeks of age 34.9% (29/83) and 39.7%(29/73) respectively. However, there was no significant difference (p-value>0.05) between age groups in the seroprevalence of IBDV. The study revealed higher prevalence of in female (40.4%) than male (35.8%) though sex doesn’t have significant effect on the occurrence of (Infectious bursal disease) in the study area (p-value > 0.05). In conclusion, the higher prevalence reported in this study indicates that the disease is widely distributed in backyard chicken production system and one of the potential threats for poultry production in the study areas and hence an urgent control and intervention measures should be implemented.

Key words: Backyard Chicken Production, Infectious Bursal Disease (IBD), Sebeta Hawas, Sero-prevalence

Sero-prevalence of Newcastle Disease in Backyard Chickens in Sebata Hawas District, Central Ethiopia

 

Tilahun Sori1, Amare Eshetu1, Asamanew Tesfaye2

AbebeGaroma2 and Shimelis Mengistu1

 

 

1College of Veterinary Medicine, Haramaya University, P.O. Box: 138, Dire Dawa, Ethiopia,

 

 2National Animal Health Diagnostic and Investigation Center, Sebata, Ethiopia

 

 

Abstract

The study was conducted in Sebata Hawas District, Oromia Region, Central Ethiopia with the objective of determining the sero-prevalence of Newcastle disease (ND) in backyard chickens using blocking-enzyme linked immunosorbent assay from November, 2014 to March, 2015. A total 344 chicken sera were collected from five randomly selected peasant associations (PA) for this study. An overall sero-prevalence of 11.34% (95% CI: 8.19-15.17%) of the Newcastle disease was recorded in the study area. The highest sero-prevalence 20% (95% CI: 12.83-28.93) was recorded at Dima peasant association which is located near to market and the sero-prevalence in each PA ranges from 0% to 20%. The sero-prevalence of Newcastle disease significantly varied among peasant associations (χ2 = 21.0; P=0.00). The sero- prevalence of Newcastle disease in cross and local breeds of chickens were 13.9% and 10.7% respectively and the difference was not significantly varied between breeds of chickens =0.59; P=0.44). Similarly, no significant difference in sero prevalence was observed between female and male; young and adult chickens.

 

Key words: Poultry, Traditional, Peasant Association, Newcastle Disease Sero-Prevalence

Infectious Laryngotracheitis Virus in Commercial and Backyard Chicken Production Systems in Central and South Ethiopia (First report)

 

Asamenew Tesfaye1*, Mesfin Sahle1Teshal Sori2,
Tadewos Kassa1Abebe Garoma1Tafese Koran1,
Chala Dima1,Chala Guyassa1Hailemariam Hilu1,
Sintayehu Guta1, Fanose Tadesse2

1National Animal Health Diagnostic and Investigation Center (NAHDIC), Sebeta, Ethiopia

2Ministry of Agriculture and Livestock Resource (MAL), Addis Ababa, Ethiopia

 

3Addis Ababa University, College Veterinary Medicine and Agriculture, Bishoftu, Ethiopia

 

 Abstract

Infectious laryngotracheitis virus (ILT) affects the respiratory tracts of chickens with profound effects in the world poultry industry. The aims of this study are to determine the prevalence and risk factors associated with ILT. The overall prevalence for ILT was 19.4% of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial and backyard poultry production systems, respectively. The prevalence was significantly different between commercial and backyard poultry production systems (P < 0.05). Study areas, breed, and purpose had no significant effect on the prevalence of ILT in commercial production systems. However, study areas significantly affect (P < 0.05) the prevalence in backyard production systems. The mean antibody titer was significantly higher (P < 0.05) in backyard production system (mean = 1209.9) over commercial production systems (mean = 334.1). As the first report in Ethiopia, this study revealed that ILT is prevalent in the country with a higher prevalence in chickens raised in backyard production systems. This indicates further studies are encouraged to determine the role of backyard chickens in the epidemiology of ILT in Ethiopia and develop vaccine(s) to prevent and control the disease.

Key words: Backyard, Commercial, ILT, Prevalence

Four Serotypes of Infectious Bronchitis Virus are Widespread in Unvaccinated Backyard Chicken and Commercial Farms in Ethiopia

 Tesfaye A1, Kassa T1,Mesfin S1, Garoma A1, Koran T1, Dima C1,Guyassa C1, Hailu H2 and Teshale S3

 

1National Animal Health Diagnostic and Investigation Center (NAHDIC), Sebeta, Ethiopia

2Ministry of Agriculture and Livestock Resource (MAL), Addis Ababa, Ethiopia

 

3Addis Ababa University, College Veterinary Medicine and Agriculture, Bishoftu, Ethiopia

 

 Abstract

Avian infectious bronchitis is highly contagious disease of respiratory, urogenital and reproductive tissues of chicken causing considerable losses due to death, egg drop and reduced production. Little information is available on infectious bronchitis in chicken in Ethiopia. The objectives of this study were to estimate seroprevalence of infectious bronchitis and identify the serotypes of infectious bronchitis virus infecting chicken in the country. A total of 711 serum samples were collected from chicken reared under ten commercial and six backyard farms in Oromia and Southern Nations Nationalities and People’s Regional States. The presence of antibody against infectious bronchitis virus was detected using standard quantitative indirect ELISA while the serotypes of the virus were identified by hemagglutination inhibition test. Out of the 711-chicken tested 502 (70.60%; CI: 67.11, 73.93) of them were found positive for anti-infectious bronchitis virus antibody. The prevalence was 68.75% (341/496; CI: 64.47, 72.81) and 74.88% (161/215; CI: 68.53, 80.53) in chicken raised under commercial settings and backyard systems, respectively. Four serotypes of infectious bronchitis virus namely M41, D-274, 793B and Qx were identified from unvaccinated backyard and commercial farms. In conclusion this study revealed that the four serotypes of IBV tested are widespread in many backyard and commercial farms in Ethiopia. The seroprevalence observed is high in both commercial and backyard chicken farms.Keywords: Infectious bronchitis; IBV; Indirect ELISA; Hemagglutination inhibition assay; Backyard; Chicken

Correlation Analysis of IGY Titer between Chickens and Parent Broiler Breeder Immunized Against Infectious Bursal Disease Virus

 

Asamenew Tesfaye, Rekik Getahun and Haileleul
Negussie

 

 

1National Animal Health Diagnostic and Investigation Center (NAHDIC), P.O. Box 04, Ethiopia2Ethiopia 

2Netherlands Trade for Agricultural Growth (ENTAG), P.O. Box 1234, Ethiopia3Addis Ababa University,

3Collage of Veterinary Medicine and Agriculture (CVMA), P.O. Box 04, Ethiopia 


Abstract

Infectious bursal disease (IBD) affects younger chickens and it is a threat for development commercial poultry farms worldwide. The aims of this study are to determine maternal antibody titer and its associate with the age of the parent breeder consequently to estimate the proper age for vaccination. Sera samples were collected from 75 parent breeders and 75 of their progeny (3 days old) at monthly interval for three consecutive months and analyzed using Indirect IDXX IBD ELISA kits. Questionnaire was also used to generate information regarding the application of vaccines against IBD.The association between parent and chicks antibody titer were statistically significant (p = 0.00) for both farms and also positively correlated at r = 0.87 and r = 0.58 for Alema and ELFORA, respectively. However, age has no association (p>0.05) with the level of antibody titer in chicken and parent breeder in both farms. Optimum date of vaccination was calculated as15th and 19th day and 14th and 19th day post hatch for ELFORA and Alema farms, respectively. The percentage coefficient of variation (CV %) was greater than 30% which indicates poor uniformity in the antibody titer; therefore, booster vaccination was mandatory. Based on questionnaire survey, 75% of medium scale poultry farms use domestic vaccines whereas the reaming uses imported vaccines. However, 100% of large scale commercial poultry farms relay on imported vaccines from European countries. All farms vaccinated there chickens based on the recommendation of manufacturers i.e., none was based on MDA titer. About 70 and 80% of medium scale and commercial farms had IBD outbreak in the last 3 years, respectively, in which 58.3% thought it was due to vaccine failure. The level of antibody titer in the progeny was associated with antibody titer in the parent breeder. Therefore, proper vaccination to parent breeder and designing proper vaccination schedules based on the MDA should be encouraged.

Keywords: CV (%), IBD, MDA, titer

Status of Humoral Immunity against Newcastle Disease Virus in Commercial Poultry Farms in Ethiopia

 

Asamenew Tesfaye1, Rediet Belayneh1, Asegedech Sirak1, Gizat Almaw1, Tadewos Kassa1, Hassen Chaka1, Teshale S2*

 

 

 1College of Veterinary Medicine, Haramaya University, P.O. Box: 138, Dire Dawa, Ethiopia,

 2National Animal Health Diagnostic and Investigation Center, Sebata, Ethiopia

 

 

Abstract

Vaccination is the method of choice for control of Newcastle disease in developing countries. A cross-sectional survey was conducted in six commercial poultry farms to assess their immune status against Newcastle disease in Ethiopia. In addition, follow up study was carried out in 210-day old chickens belonging to Rose, Lohmann brown and Sasso breeds to compare their response to HB1 and La Sota vaccines. Blood samples were collected from 75-day-old chickens (25 chickens from each breed) to assess the level of maternally derived antibody titer before vaccine was given. Blood samples were collected fortnightly after the first and booster vaccinations. Haemagglutination inhibition assay was used to assess the level of antibody in serum samples collected. Only two of the six farms investigated maintained good flock immunity (≥85% level of protection) with low percent-age geometric coefficient of variation (4.9%-14.4%). The maternally derived antibody titre was significantly higher in Sasso breeds (134.4±1.14) followed by Ross (92.2±1.14) and Lohmann brown (68.6±1.35). The level of anti-Newcastle disease virus antibody after the first vaccination was 24.6±1.2 in Lohmann brown, 29.3±2 in Sasso and 34.5±1.1 in Ross breeds. The antibody titer was 30.9±1.3 in Lohmann brown, 29.4±1.2 in Sasso and 33.1±1.2 in Ross breeds after booster vaccination. In conclusion the maternally derived antibody level was sufficient to protect chickens from infection during early age but the flock immunity and post vaccination antibody level was low suggesting the investigation of alternative vaccination schedules for better prevention and control of Newcastle disease than the current one (day 0, day 7 and day 21).

 

Keywords: %GCV; Breed; Flock Immunity; HI; MDA; NDV

Sequence-based Comparison between Field Isolates and Vaccine Strains of Infectious Bursal Disease Virus Revealed Amino acid Mismatch in the Immune Dominant VP2 Protein in Ethiopia

 

Dereje Shegu1, Teshale Sori2*, Asaminew Tesfaye1, Alebachew Belay3, Hawa Mohammed3,Teferi Degefa3, Belayneh Getachew3, Takele Abayneh3, Esayas Gelaye3*

 

1National Animal Health Diagnostic and Investigation Center, P.O.Box 04, Sebeta, Ethiopia

2Addis Ababa University College of Veterinary Medicine and Agriculture, Department of

Clinical Studies, P.O.Box 34, Bishoftu, Ethiopia

3National Veterinary Institute, Research and Development Department, P.O.Box 19, Bishoftu, Ethiopia

 

Abstract

Sequence based comparison of amino acid mismatch was investigated between vaccine strains and field isolates of infectious bursal disease viruses. Virus isolation was done in chicken embryo fibroblast (DF-1) cell from pooled samples of bursa collected from nine outbreaks. Identification of the virus strains was performed by comparing the deduced amino acid sequence between positions 232 and 446 of the immune dominant VP2 epitope. An outbreak affecting 30,250 chickens in five localities inflicting an overall mortality of 47.87% was observed. All the pooled samples yielded positive results. Molecular analysis revealed a 645bp DNA fragment. Phylogenetic analysis revealed clustering of the isolates into very virulent infectious bursal disease virus. The deduced amino acid sequence showed that the present isolates have identical amino acid sequence with the European very virulent strains such as UK 661 and DV 86 except at position 222 but differ from the vaccine strains used in Ethiopia suggesting the possible introduction of the virus to Ethiopia from Europe. Our study demonstrated widespread occurrence of very virulent strains of infectious bursal disease virus in poultry farms in Ethiopia and the need to evaluate the existing vaccines against the circulating field viruses.

 

Keywords: Ethiopia, IBDV field isolates, poultry, sequencing, vaccine, VP2 gene

The Occurrence and Identification of Culicoides Species in the Western Ethiopia

 

1Tesfaye Mulatu and 2AbdisaHailu   

1National
Animal Health Diagnostic and Investigation Center, Sebeta, Ethiopia

2
Hawassa University, Hawassa, Ethiopia

 

 

Abstract

A study using convenience sampling method was conducted from of December/2015 to January /2016 with the aim to detect the occurrence of Culicoides and identify the species in the Western parts of Ethiopia; in Dima, Mizan, Bita and Moyale districts. A total of 902 Culicoides midges 194 (21.5%) in Dima, 533 (59%) in Mizan, 130 (14.4%) in Bita and 45 (4.9%) in Moyale were captured during collection made using light traps. From the captured Culicoides midges 225 (25% of total midges caught) were sorted based on morphological features of Culicoides and 6 species were identified. From the identified six species of Culicoides; C. milnei (28.4%) scored the highest count, followed by C. zuluensis (27.1), C.  imicola (16.9%),  C. neavei  (13.8%), C. fulvithorax (8%) and C. isioloensis with the  list  scored  count  (5.8%),  in  the  overall  studied  areas and the difference in percentage between the species within the districts was found to be significant (P < 0.05). Further studies are needed in order to fully understand the role of these Culicoides species in the transmission of arboviruses, to determine the seasonal dynamics of these species and to design the preventive and control strategies of such a vector.

Key words: Culicoides Midges, Light Traps, Western Ethiopia, Arboviruses

Global Distribution of Culicoides imicola, a Major Vector of Bluetongue, Schmallenberg and African Horse Sickness Viruses

Samson Leta Regassa1*Eyerusalem Fetene1Tesfaye Mulatu2Kebede Amenu1,Megersa Bedasa1Tariku Jibat Beyene1Haileleul Negussie1 and Crawford W. Revie3

  

1 Addis Ababa University, Ethiopia

2 National Animal Health Diagnostic and Investigation Centre (NAHDIC), Ethiopia

3 University of Strathclyde, United Kingdom

  

Abstract

Culicoides imicola is a midge species transmitting the agents of a number of viral diseases of veterinary importance, including Bluetongue, Schmallenberg, and African Horse Sickness. Climatic, social and demographic factors may impose rapid changes on the global distribution of C. imicola and allow introduction into new area. The aim of this study is to extract the global occurrence of C. imicola from available literature and to model the global distributions of C. imicola using an ensemble modeling approach by combining climatic, demographic and land cover covariates. In this study probabilistic global habitat suitability model for C. imicola was developed using an ensemble modelling technique. The modelling was implemented using R package biomod2. The models developed combine climatic, demographic and land cover covariates to predict the global distribution of C. imicola and to characterize the respective variable contribution. The following sets of input data were used in order to make accurate predictions of the distribution of this species (i) environmental and livestock distribution data which includes climatic, land cover and demographic data; and (ii) a globally comprehensive dataset of geo-positioned occurrence points for C. imicola. The study provided an updated and comprehensive global database of C. imicola occurrence, consisting of 1039 geo-positioned records from 50 countries around the world. The ensemble model performed very well and indicated high environmental suitability for C. imicola in the tropics and subtropics. The habitat suitability for C. imicola spans from South Africa to southern Europe and from Southern USA to southern China. Thirty individual models (10 algorithms x 3 evaluation runs) were generated by ‘biomod2’, 21 models scored a true skills statistics (TSS) > 0.8 (TSSaverage = 0.81). These 21 models incorporated weighted runs from RF, GAM, GLM, GBM, CTA, ANN, FDA and MARS algorithms to create a final ensemble model. The distribution of C. imicola is mainly constrained by climatic factors. In this ensemble model, mean annual minimum temperature had the highest overall contribution (42.9%), followed by mean annual maximum temperature (21.1%), solar radiation (13.6%), Annual precipitation (11%), livestock distribution (6.2%), vapor pressure (3.4%), wind speed (0.8%), and land cover (0.1%). The present study provided the most updated and detailed maps of the current global potential distributions of C. imicola using ensemble modeling technique. The result presented here is based on thinned and unbiased and the most extensive C. imicola occurrence dataset created to date, and represents the most updated description of C. imicola distribution.

 

Keywords: AHS, biomod2, Bluetongue (BT), Culicoides imicola, ensemble modelling, Schmallenberg virus