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Lumpy skin disease (LSD) is an acute or inapparent viral disease of cattle which is endemic in many African and Middle East countries. LSD is one of the major transboundary livestock diseases in Ethiopia. A cross-sectional study using multistage cluster sampling was undertaken in central and north-western parts of Ethiopia with the objectives to estimate seroprevalence and to identify and quantify risk factors contributing to the occurrence of the disease. A total of 2386 cattle sera were sampled from 605 herds and 30 clusters (kebeles) located in 10 districts and tested for presence of LSD virus antibodies using virus neutralization test. All the serum samples were collected from cattle having no history of LSD vaccination. The overall animal level and herd level apparent seroprevalences were 25.4% (95% CI: 23.7–27.2) and 48.9% (95% CI: 44.9-52.9), respectively and varied significantly between districts. The true animal level and herd level prevalences were estimated as 26.5% (95% CI: 24.7–28.3) and 52.6% (95% CI: 48.3–56.9), respectively. At animal level, adult age (OR = 2.44 (95% CI: 1.67–3.55) compared to calf), contact with other animals (OR = 0.41 (95% CI: 0.23-0.74), compared to no contact) and presence of water bodies (OR = 1.61 (95% CI: 1.03–2.52), compared to no such bodies) were identified as the most important risk factors in relation to testing LSD positive. The putative risk factors altitude, breed, sex, and presence of animal trade route showed no significant association with LSD sero-status. Generally, cattle population with many adult animals and that live in wet areas are at highest risk, whereas cattle in frequent contact with other animals and animal species have lower risk, potentially due to a dilution effect of vectors.

Lumpy skin disease (LSD), an infectious viral disease of cattle, causes considerable financial losses in livestock industry of affected countries. A questionnaire survey with the objectives of determining direct economic losses of LSD (mortality loss, milk loss, draft loss) and treatment costs (medication and labour cost) per affected herd, and assessing the cost effectiveness of vaccination as a means for LSD control was carried out in the central and north-western parts of Ethiopia. From a total of 4430 cattle (in 243 herds) surveyed, 941 animals (in 200 herds) were reported to be infected. The overall morbidity and mortality at animal level were 21.2% and 4.5%, and at herd level these were 82.3% and 24.3%. There was a significant difference in animal level morbidity and mortality between categories of animals. Over 94% of the herd owners ranked LSD as a big or very big problem for cattle production. A large proportion (92.2%) of the herd owners indicated that LSD affects cattle marketing. A median loss of USD 375 (USD 325 in local Zebu and USD 1250 in Holstein-Friesian local Zebu cross cattle) was estimated per dead animal. Median losses per affected lactating cow were USD 141 (USD 63 in local Zebu cows and USD 216 in Holstein-Friesian local Zebu cross cows) and, USD 36 per affected ox. Diagnosis and medication cost per affected animal were estimated at USD 5. The median total economic loss of an LSD outbreak at herd level was USD 1176 (USD 489 in subsistence farm and USD 2735 in commercial farm). At herd level, the largest component of the economic loss was due to mortality (USD 1000) followed by milk loss (USD 120). LSD control costs were the least contributor to herd level losses. The total herd level economic losses in the commercial farm type were significantly higher than in the subsistence farm type. The financial analysis showed a positive net profit of USD 136 (USD 56 for subsistence farm herds and USD 283 for commercial herds) per herd due to LSD vaccine investment. It should be noted that only the noticeable direct costs and treatment costs associated with the disease were considered in the study. Generally, vaccination is economically effective and should be encouraged.

To optimize control of an avian influenza outbreak knowledge of within-flock transmission is needed. This study used field data to estimate the transmission rate parameter (beta) and the influence of risk factors on within-flock transmission of highly pathogenic avian influenza (HPAI) H7N7 virus in the 2003 epidemic in The Netherlands. The estimation is based on back-calculation of daily mortality data to fit a susceptible-infectious-dead format, and these data were analysed with a generalized linear model. This back-calculation method took into account the uncertainty of the length of the latent period, the survival of an infection by some birds and the influence of farm characteristics. After analysing the fit of the different databases created by back-calculation, it could be concluded that an absence of the latency period provided the best fit. The transmission rate parameter (beta) from these field data was estimated at 4.50 per infectious chicken per day (95% CI: 2.68-7.57), which was lower than what was reported from experimental data. In contrast to general belief, none of the studied risk factors (housing system, flock size, species, age of the birds in weeks and date of depopulation) had significant influence on the estimated beta.

Although reduction in transmission of an agent in the host population is an important goal of many vaccinations, suitable experimental methods to measure transmission have been lacking. Therefore, we designed and tested an animal experiment to quantify transmission among vaccinated and unvaccinated animals. We used Aujeszky's disease virus (ADV) in pigs, because a serological test was available to detect infection in vaccinated pigs and because vaccination against ADV will be used in an attempt to eliminate ADV from the Netherlands. Our experiments showed that vaccinating twice with vaccine 783 significantly reduces ADV transmission. In unvaccinated groups, the estimated maximum number of secondary cases per infectious individual, i.e. the basic reproduction ratio R0, was 10.0. In contrast, the reproduction ratio for the vaccinated groups R, i.e. the average number of secondary cases per infectious individual in a totally vaccinated population, was 0.5. These results show that it is possible to measure transmission experimentally. Therefore, such measurements should be obtained for all vaccines that are intended to eliminate agents causing animal diseases, either on a single farm or in a whole country.

Computer-simulation models of infections can easily incorporate heterogeneity among animals (important for the effect of control measures) by allocating animals to various classes. These classes are termed ‘states’ and the change from one state to another, during a unit of time, is termed a ‘transition’. Hence, most computer models are state-transition models. Using a fairly universal representation state-transition models, we derived an analytic expression (a formula) for the basic reproduction ratio of infection (R0), i.e. the number of cases caused by one typical infectious animal. When R0>1, the infection can spread; when R0