The authors of a study on the bubonic plague in Oran stress that the disease "is primarily a bacterial zoonosis affecting rodents. It is caused by Yersinia pestis and is transmitted from animal to animal by fleas. Humans usually become infected through the bite of an infected rodent flea." The sanitary control measure instituted by the public health authority was chemical in nature: "Intra- and peridomestic spraying with permethrin was conducted. Deltamethrin was dusted on the tracks and around the burrows of rodents located in a radius of 10 km around the dwelling of the patients. Uncontrolled killing of rats was prohibited. "A large proportion of viral pathogens that have emerged recently in humans are considered to have originated from various animal species. This is shown by several recent epidemics such as, avian flu, Ebola, monkeypox, and Hanta viruses. There is evidence to suggest that some diseases can potentially be re-introduced to human populations through animal hosts after they have been eradicated in humans. There is a risk of this phenomenon occurring with morbilliviruses as they can readily cross species barriers. CST can also have a significant effect on produce industries. Genotype VI-Avian paramyxovirus serotype 1 (GVI-PMV1) is a virus that arose through cross-species transmission events from Galliformes (i.e. chicken) to Columbiformes, and has become prevalent in the poultry industry.CST of rabies virus variants between many different species populations is a major concern of wildlife management.
Models for CST prediction will vary depending on what parameters need to be accounted for when constructing the model. Most parsimonious reconstruction (MPR)
Parsimony is the principle in which one chooses the simplest scientific explanation that fits the evidence. In terms of building phylogenetic trees, the best hypothesis is the one that requires the fewest evolutionary changes. Using parsimony to reconstruct ancestral character states on a phylogenetic tree is a method for testing ecological and evolutionary hypotheses. This method can be used in CST studies to estimate the number of character changes that exist between pathogens in relation to their host. This makes MPR useful for tracking a CST pathogen to its origins. MPR can also be used to the compare traits of host species populations. Traits and behaviours within a population could make them more susceptible to CST. For example, species which migrate regionally are important for spreading viruses through population networks.Despite the success of parsimony reconstructions, research suggests they are often sensitive and can sometimes be prone to bias in complex models. This can cause problems for CST models that have to consider many variables. Alternatives methods, such as maximum likelihood, have been developed as an alternative to parsimony reconstruction. Using genetic markers
Two methods of measuring genetic variation, variable number tandem repeats (VNTRs) and single nucleotide polymorphisms (SNPs), have been very beneficial to the study of bacterial transmission.