Epidemiology of Brucellosis
Epidemiological surveillance, Phylogeography
Epidemiological surveillance is the ongoing and systematic collection, analysis and interpretation of health-related data. Guidelines have been proposed by FAO (2003). The process involves describing and monitoring health events in populations of humans or animals, or, in the case of a zoonosis such as brucellosis, both. For example, typical questions to which a surveillance system might be asked to provide answers include:
-
How extensive is the infection, and when and where is it occurring?
-
Which species of Brucella are involved?
-
Which animal species are involved?
-
Is the prevalence and incidence (human or animal) decreasing, increasing or static?
-
When epidemics occur, what is the source, and how is the agent being transmitted?
-
What strategies should be adopted to control, prevent and ultimately eradicate the infection?
-
What are the knowledge, attitudes and practices of the populations affected?
-
What laboratory or field research needs to be undertaken?
More recently, the Centers for Disease Control and Prevention (CDC) and FAO have been collaborating to develop the Brucellosis One Health Guidance and Tools (BOHGAT), a set of complementary resources that use a multisectoral, One Health approach to assist counties in preventing, controlling and eliminating brucellosis in animals and people. Resources within the BOHGAT that are nearing finalization include the Stepwise Approach for the Progressive Control of Brucellosis (SAPCB) and the Staged Tool for the Elimination of Brucellosis (STEB).
Phylogeography is the study of the spatial arrangement of genealogical lineages, especially within and among conspecific populations and closely related species. One of several new types of nuclear data stemming from next-generation sequencing involves the recovery of single nucleotide polymorphismes (SNPs) from many thousands of unlinked nuclear genomic regions, even in nonmodel species. SNPs are increasingly being used to supplement more traditional phylogeographic datasets based on cytoplasmic genomic sequences or allelic profiles at relatively small numbers of microsatellite loci. The term “landscape genetics” has blossomed in recent years into a recognizable and popular research arena, purportedly forming a needed bridge between landscape ecology and population genetics (much as the field of phylogeography attempted to bridge phylogenetics and population genetics; Avise et al, 2016).
One Health Concept
Between animal and human medicine there are no dividing lines—nor should there be. Rudolf Virchow, 1856
In 2018, an Operational Framework supported by the World Bank described One Health as: a collaborative approach for strengthening systems to prevent, prepare, detect, respond to, and recover from primarily infectious diseases and related issues such as antimicrobial resistance that threatens human health, animal health, and environmental health collectively, using tools such as surveillance and reporting with an endpoint of improving global health security and achieving gains in development.
For more information, see Operational Framework for Strengthening Human, Animal, and Environmental Public Health Systems at their Interface (Berthe et al, 2018).
Comparisons of brucellosis between human and veterinary medicine
Hull & Schumaker, 2018. Infect Ecol Epidemiol. 2018 Jul 24;8(1):1500846.
Brucellosis is the world’s most widespread zoonosis, but also ranks as one of the seven most neglected diseases, according to the World Health Organization. Countries with the highest incidence of human brucellosis are Syria (1,603.4 cases per 1,000,000 individuals), Mongolia (391.0), and Tajikistan (211.9).
Surveillance on animal populations is lacking in many developed and developing countries. According to the World Animal Health Information Database, Mexico had the largest number of reported outbreaks, 5,514 in 2014. Mexico is followed by China (2,138), Greece (1,268), and Brazil (1,142; Hull & Schumaker, 2018).