Reflections on IDEAL: What we have learnt from a unique calf cohort study.

The year 2020 marks a decade since the final visit was made in the 'Infectious Diseases of East African Livestock' (IDEAL) project. However, data generation from samples obtained during this ambitious longitudinal study still continues. As the project launches its extensive open-access database and biobank to the scientific community, we reflect on the challenges overcome, the knowledge gained, and the advantages of such a project. We discuss the legacy of the IDEAL project and how it continues to generate evidence since being adopted by the Centre for Tropical Livestock Genetics and Health (CTLGH). We also examine the impact of the IDEAL project, from the authors perspective, for each of the stakeholders (the animal, the farmer, the consumer, the policy maker, the funding body, and the researcher and their institution) involved in the project and provide recommendations for future researchers who are interested in running longitudinal field studies.

Endemic foot and mouth disease: pastoral in-herd disease dynamics in sub-Saharan Africa.

Foot and mouth disease (FMD) burden disproportionally affects Africa where it is considered endemic. Smallholder livestock keepers experience significant losses due to disease, but the dynamics and mechanisms underlying persistence at the herd-level and beyond remain poorly understood. We address this knowledge gap using stochastic, compartmental modelling to explore FMD virus (FMDV) persistence, outbreak dynamics and disease burden in individual cattle herds within an endemic setting. Our analysis suggests repeated introduction of virus from outside the herd is required for long-term viral persistence, irrespective of carrier presence. Risk of new disease exposures resulting in significant secondary outbreaks is reduced by the presence of immune individuals giving rise to a period of reduced risk, the predicted duration of which suggests that multiple strains of FMDV are responsible for observed yearly herd-level outbreaks. Our analysis suggests management of population turnover could potentially reduce disease burden and deliberate infection of cattle, practiced by local livestock keepers in parts of Africa, has little effect on the duration of the reduced risk period but increases disease burden. This work suggests that FMD control should be implemented beyond individual herds but, in the interim, herd management may be used to reduced FMD impact to livestock keepers.

Implementation of high coverage mass rabies vaccination in rural Uganda using predominantly static point methodology.

Despite successful eradication programmes in many regions, rabies remains responsible for approximately 60,000 human deaths annually, and no country in Africa is rabies-free. Dogs are the principal reservoir of the virus in Africa and the World Health Organisation recommends that at least 70% of the dog population be vaccinated in order to break the transmission cycle. Most attempts at mass rabies vaccinations in Africa have failed to vaccinate high numbers of dogs at a high coverage. Successful studies have often used a door-to-door (DTD) approach, which is logistically challenging and expensive compared to a static point (SP) approach. Mission Rabies has successfully implemented a combined SP and DTD method in cities in India and Malawi. This campaign used a combined methodology in rural Uganda, starting with a SP campaign, followed by a DTD campaign, and then subsequent transect surveys to assess vaccination coverage. This was facilitated by the use of a smartphone application which recorded all vaccinations and survey responses along with their Global Positioning System location. A total of 4172 dogs were vaccinated in 7 days, attaining an estimated 88.4% coverage. This campaign is of particular note as 95.9% of the vaccinations were performed at SPs. The human-to-dog ratio was 4.9 with a mean dogs per house of 1.2. Most dogs were owned (93.7%). This demonstrates that high-number, high-coverage vaccination is achievable in rural Uganda and provides data that may refine future campaign approaches.

Bluetongue and epizootic haemorrhagic disease virus in local breeds of cattle in Kenya.

The presence of bluetongue virus (BTV) and Epizootic Haemorrhagic Disease virus (EHDV) in indigenous calves in western Kenya was investigated. Serum was analysed for BTV and EHDV antibodies. The population seroprevalences for BTV and EHDV for calves at 51 weeks of age were estimated to be 0.942 (95% CI 0.902-0.970) and 0.637 (95% CI 0.562-0.710), respectively, indicating high levels of circulating BTV and EHDV. The odds ratio of being positive for BTV if EHDV positive was estimated to be 2.57 (95% CI 1.37-4.76). When 99 calves were tested for BTV and EHDV RNA by real-time RT-PCR, 88.9% and 63.6% were positive, respectively. Comparison of the serology and real-time RT-PCR results revealed an unexpectedly large number of calves that were negative by serology but positive by real-time RT-PCR for EHDV. Eight samples positive for BTV RNA were serotyped using 24 serotype-specific real-time RT-PCR assays. Nine BTV serotypes were detected, indicating that the cattle were infected with a heterogeneous population of BTVs. The results show that BTV and EHDV are highly prevalent, with cattle being infected from an early age.

Urban domestic dog populations as a source of canine distemper virus for wild carnivores in the Coquimbo region of Chile.

Urban areas can support dog populations dense enough to maintain canine distemper virus (CDV) and can be a source of infection for rural dogs and free-ranging carnivores. The aim of this study was to investigate the relationships between urban and rural domestic dog and wild carnivore populations and their effects on the epidemiology of CDV to explain retrospectively a CD outbreak in wild foxes in 2003. From 2005 to 2007 a cross-sectional household questionnaire survey was conducted in Coquimbo and Ovalle cities, in three towns and in rural sites along two transects from these cities to the Fray Jorge National Park (FJNP) in the Coquimbo region, Chile. Blood samples were collected from unvaccinated dogs at surveyed households and from free-ranging foxes in rural areas along the transects. The seroprevalence of CDV in domestic dogs was higher in urban than in rural areas and in the later was highest in dogs born before 2001-2002. The seroprevalence of CDV in foxes was higher in areas closer to human settlements. A high seroprevalence in dogs born before 2001-2002 further supports a link between CDV patterns in rural dog and fox populations. In our study area, urban dogs are proposed to be the source of CDV infection to wild carnivores. The large dog population size and density detected in Coquimbo and Ovalle provides optimal conditions for maintaining a large and dense susceptible population of dogs, which can act as a reservoir for highly infectious diseases and could have been the source of infection in the CD outbreak in wild foxes.

Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission.

A cross-sectional household questionnaire survey was conducted along two transects (80 and 45km long) from Coquimbo and Ovalle cities to the Fray Jorge National Park (FJNP) in the Coquimbo region of Chile in 2005-2007 to investigate the demography of dogs in the context of a study of canine infectious diseases. Data were collected on the number of dogs per household, fecundity, mortality, and sex and age distribution. The results from 1021 households indicated that dog ownership was common, with a higher proportion of households owning dogs in rural areas (89%), than in towns (63%) or cities (49%). Dog density ranged from 1380+/-183 to 1509+/-972 dogs km(-2) in cities, from 119+/-18 to 1544+/-172 dogs km(-2) in towns, and from 1.0+/-0.4 to 15.9+/-0.4 dogs km(-2) in rural sites. The dog population was estimated to be growing at 20% in cities, 19% in towns and 9% in rural areas. The human:dog ratio ranged from 5.2 to 6.2 in cities, from 2.3 to 5.3 in towns, and from 1.1 to 2.1 in rural areas. A high percentage of owned dogs was always allowed to roam freely in the different areas (27%, 50% and 67% in cities, towns and rural areas, respectively). Observations of free-roaming dogs of unknown owner were reported from a greater proportion of respondents in cities (74%), followed by towns (51%) and finally by rural areas (21%). Overall only 3% of dogs had been castrated. In addition, only 29% of dogs were reported to have been vaccinated against canine distemper virus (CDV) and 30% against canine parvovirus (CPV). The higher population size and density, higher growth rate and a higher turnover of domestic dogs in urban than in rural areas and the poorly supervised and inadequately vaccinated dog populations in urban areas suggest that urban areas are more likely to provide suitable conditions for dogs to acts as reservoirs of pathogenic infections.

Foot and mouth disease and livestock husbandry practices in the Adamawa Province of Cameroon.

Foot and mouth disease (FMD) is a highly contagious viral disease of even-toed ungulates and is endemic in most of the tropics. A cross-sectional study using a stratified, two-stage random sample design was undertaken in the Adamawa Province of Cameroon. The objectives were to measure the reported herd-level prevalence of FMD and a range of husbandry practices important for its transmission. The owner-reported prevalence for the previous 12 months was 57.9% (50.4-65.4%), although there was a significant variation across the Province. During the previous dry season, 46.5% (38.6-54.4%) of herds had gone on transhumance. Herds had high numbers of contacts with other herds while on transhumance (98.6%), at pasture (95.8%) and at night (74.4%), with medians of 7-10, 4-6 and 1-3 daily contacts, respectively. The high level of endemic FMD and potential for disease spread presents a significant challenge for control and eradication. Locally sustainable methods need to be developed upon which larger regional control programmes could be built in the future.