Infectious disease surveillance in animal movement networks: An approach based on the friendship paradox.

The network of animal movements among livestock premises is an important topological structure for the spread of infectious diseases. The central focus of this study was to analyze strategies for selecting premises based on the friendship paradox ("your friends have more friends than you do") - in which premises that neighbor randomly selected premises are sampled for surveillance or control - to determine whether these strategies are viable alternatives for the surveillance and control of diseases in scenarios with insufficient data on animal movement. To test the effectiveness of these strategies, we performed three sets of simulations. In the first set, we examined the risk of spreading an infectious disease using the cattle movement network of the state of Mato Grosso, Brazil. All tested strategies based on the friendship paradox have comparable performance to the hub control strategy (controlling premises that sold more animals) and superior performance to random sampling in terms of both reducing the risk of purchasing infected animals and the number of premises that need to be controlled. In the second and third sets of simulations, we observed that the friendship paradox strategies were more sensitive than the random sampling strategy to detect cases and disease, respectively. The survey of the entire animal movement network to identify animal premises with a key role in trade is not always possible, either because the data are insufficient or because informal trade is significant. If surveying the network is not possible, all approaches based on knowledge of the network become useless. As an alternative, knowing that there is a hidden movement network that follows rules inherent to all networks, such as the friendship paradox, can be used to our advantage. Strategies based on the friendship paradox do not assume knowledge of the animal movement network and therefore may be viable alternatives for the surveillance or control of infectious diseases in the absence of network information, thus optimizing the use of human and financial resources.

Uso de sistemas de informação geográfica em campanhas de vacinação contra a raiva / Uso de sistemas de información geográfica en campañas de vacunación contra la rabia / Use of geographic information systems in rabies vaccination campaigns

OBJETIVO: Desenvolver método para planejamento e avaliação de campanhas de vacinação contra a raiva animal. MÉTODOS: O desenvolvimento da metodologia baseou-se em sistemas de informação geográfica para estimar a população e a densidade animal (canina e felina) por setores censitários e subprefeituras do município de São Paulo, em 2002. O número de postos de vacinação foi estimado para atingir uma dada cobertura vacinal. Foram utilizadas uma base de dados censitários para a população humana, e estimativas para razões cão:habitante e gato:habitante. RESULTADOS: Os números estimados foram de 1.490.500 cães e 226.954 gatos em São Paulo, uma densidade populacional de 1.138,14 animais domiciliados por km². Foram vacinados, na campanha de 2002, 926.462 animais, garantindo uma cobertura vacinal de 54 por cento. O número total estimado de postos no município para atingir uma cobertura vacinal de 70 por cento...

OBJECTIVE: To develop a method to assist in the design and assessment of animal rabies control campaigns. METHODS: A methodology was developed based on geographic information systems to estimate the animal (canine and feline) population and density per census tract and per subregion (known as "Subprefeituras") in the city of São Paulo (Southeastern Brazil) in 2002. The number of vaccination units in a given region was estimated to achieve a certain proportion of vaccination coverage. Census database was used for the human population, as well as estimates ratios of dog:inhabitant and cat:inhabitant. RESULTS: Estimated figures were 1,490,500 dogs and 226,954 cats in the city, i.e. an animal population density of 1138.14 owned animals per km². In the 2002 campaign, 926,462 were vaccinated, resulting in a vaccination coverage of 54 percent. The estimated number of vaccination units to be able to reach a 70 percent...

OBJETIVO: Desarrollar método para planificación y evaluación de campañas de vacunación contra la rabia animal. MÉTODOS: El desarrollo de la metodología se basó en sistemas de información geográfica para estimar la población y la densidad animal (canina y felina) por sectores censales y sub-prefecturas del municipio de Sao Paulo (Sureste de Brasil), en 2002. El número de puestos de vacunación fue estimado para atender una determinada cobertura de vacunación. Se utilizaron una base de datos censales para la población humana, y estimativas para razones perro: habitante y gato: habitante. RESULTADOS: Los números estimados fueron de 1.490.500 perros y 226.954 en Sao Paulo, una densidad poblacional de 1.138,14 animales domiciliados por km2. Fueron vacunados, en la campaña de 2002, 926.462 animales, garantizando una cobertura de vacunas de 54 por ciento. El número total estimado de puestos en el municipio para atender una cobertura de vacunación de 70 por ciento...

Use of geographic information systems in rabies vaccination campaigns.

OBJECTIVE: To develop a method to assist in the design and assessment of animal rabies control campaigns. METHODS: A methodology was developed based on geographic information systems to estimate the animal (canine and feline) population and density per census tract and per subregion (known as "Subprefeituras") in the city of São Paulo (Southeastern Brazil) in 2002. The number of vaccination units in a given region was estimated to achieve a certain proportion of vaccination coverage. Census database was used for the human population, as well as estimates ratios of dog:inhabitant and cat:inhabitant. RESULTS: Estimated figures were 1,490,500 dogs and 226,954 cats in the city, i.e. an animal population density of 1138.14 owned animals per km(2). In the 2002 campaign, 926,462 were vaccinated, resulting in a vaccination coverage of 54%. The estimated number of vaccination units to be able to reach a 70%-vaccination coverage, by vaccinating 700 animals per unit on average, was 1,729. These estimates are presented as maps of animal density according to census tracts and "Subprefeituras". CONCLUSIONS: The methodology used in the study may be applied in a systematic way to the design and evaluation of rabies vaccination campaigns, enabling the identification of areas of critical vaccination coverage.