Relationship between levels of very virulent MDV in poultry dust and in feather tips from vaccinated chickens.

To assess the effect of various vaccine strains on replication and shedding of virulent Marek's disease virus from experimentally infected chickens, quantitative PCR (q-PCR) methods were developed to accurately quantify viral DNA in infected chickens and in the environment in which they were housed. Four groups of 10 chickens, kept in poultry isolators, were vaccinated at 1 day old with one of four vaccines covering each of the three vaccine serotypes, then challenged with very virulent MDV strain Md5 at 8 days of age. At regular time-points, feather tips were collected from each chicken and poultry dust was collected from the air-extract prefilter of each isolator. DNA was extracted from feather and dust samples and subjected to real-time q-PCR, targeting the U(S)2 gene of MDV-1, in order to measure Md5 level per 10(4) feather tip cells or per microgram of dust. Accuracy of DNA extraction from dust and real-time q-PCR were validated by comparing either q-PCR cycle threshold values or the calculated MDV genome level; for use in q-PCR, DNA was extracted from serial dilutions of MDV-infected dust diluted with noninfected dust, or DNA from MDV-infected dust was diluted with DNA from noninfected dust. The results confirmed the accuracy and sensitivity of dust DNA extraction and subsequent q-PCR and showed that differences in virus levels between dust samples truly reflect differences in shedding. Vaccination delayed both replication of Md5 in feather tips and shedding of Md5. First detection of Md5 in feather tips always preceded or coincided with first detection in dust in each group. pCVI988 and HVT+SB-1 were the most efficient vaccines in reducing both replication and shedding of Md5. There was close correlation between mean virus level in feathers of each group and mean virus level in the dust shed by that group. This relationship was similar in each of the vaccinated groups, demonstrating that measurement of the virus in dust can be used to monitor accurately both the infection status of the chickens and environmental contamination by MDV.

Epidemiological Characteristics and Economic Impact of Lumpy Skin Disease, Sheeppox and Goatpox Among Subsistence Farmers in Northeast Nigeria.

Lumpy skin disease (LSD), sheeppox (SP), and goatpox (GP) are contagious viral infections, affecting cattle (LSD), sheep and goats (SP and GP) with highly characteristic clinical signs affecting multiple body systems. All three diseases are widely reported to reduce meat, milk, wool and cashmere production although few studies have formally evaluated their economic impact on affected farms. This study aimed to estimate the economic impact and epidemiological parameters of LSD, SP, and GP among backyard and transhumance farmers in northeast Nigeria. A retrospective study was conducted on herds and flocks affected between August 2017 and January 2018 in Bauchi, Nigeria. Herds and flocks were diagnosed based on clinical signs and information was collected once the outbreak concluded using a standardized questionnaire. Data were collected from 99 farmers (87 backyard and 12 transhumance). The median incidence risk and fatality rate were 33 and 0% in cattle, 53 and 34 % in sheep; 50 and 33% in goats, respectively, with young stock having higher incidence risk and fatality rates than adults. Almost all farmers (94%) treated affected animals with antibiotics, spending a median of US$1.96 (min US$0.19-max US$27.5) per herd per day. Slaughtering or selling affected animals at low prices were common coping strategies. Farmers sold live cattle for 47% less than would have been sold if the animal was healthy, while sheep and goats were sold for 58 and 57% less, respectively. Milk production dropped 65% when cows were clinically affected and 35% after they recovered. Cattle lost a median of 10% of their live weight and sheep and goats lost 15%. Overall economic losses at farm level range from US$9.6 to US$6,340 depending on species affected and production system. Most of the farmers (72%) had not replaced all affected animals at the time of the study. Livestock markets were the most common place to sell affected animals and buy replacements, suggesting these are likely hubs for spreading infections. This study confirms the immediate and long-lasting impact of these diseases on subsistence farmers' livelihoods in North-East Nigeria and suggests potential mechanisms for targeted control.