Environmental Factors Are Connected to Human Lyme Disease Infections in California

Lyme disease can be spread by tick bites. However, even knowing where these ticks reside does not guarantee that the disease they carry will infect humans.

It's merely a small component of a bigger picture that also takes into account human behavior and the routines of the parasite's carriers.

Mapping Lyme disease west

(Photo : Erik Karits/Unsplash)

At least in California, the ecology of the small mammals that ticks feed on can be used to explain the prevalence of human Lyme disease, according to researchers at UC Santa Barbara, as per ScienceDaily.

Therefore, by observing how these animals-along with their tick parasites-respond to shifting climatic conditions and land use, researchers and public health authorities may be able to forecast future disease risks.

Environmental Research Letters published the results.

According to co-author Sam Sambado, a doctoral student in the Department of Ecology, Evolution, and Marine Biology, this study is distinctive because it attempts to quantify the relationships between climate, mammals, ticks, and humans.

This type of research calls for a variety of data types, research methodologies, and academic backgrounds.

By way of tick bites, the bacterium Borrelia burgdorferi primarily causes Lyme disease. However, the bacterium is not present at birth in the western blacklegged tick.

Only by consuming an infected host, which acts as a reservoir for the microbe, can it contract the pathogen

Although the relationship between the ecology of the tick's hosts and the spread of the disease in humans should be related, it isn't always obvious.

According to first author Andy MacDonald, an assistant professor at the Bren School of Environmental Science & Management, "it's challenging to link the ecology to the epidemiology - or where people get sick - because humans change their behavior based on risk."

Where people go, how they interact with the landscape, and whether they take precautions against tick bites all affect where people contract Lyme disease.

The team used geo-referenced locations where infected ticks had been gathered across California for this project.

After that, they used machine learning to link tick infection rates to various environmental factors, such as habitat suitability for various small mammals that can act as B reservoirs.

According to MacDonald, it is most likely for small mammals to contract an infection and then spread it to an uninfected tick.

Large mammals do not accumulate significant levels of pathogens, and the immune systems of reptiles may even eradicate the bacteria.

However, it can be challenging to translate this ecological knowledge into epidemiological insights. According to MacDonald, "We wanted to know whether this ecology was actually predictive of human disease."

Humans react behaviorally to disease risks, such as avoiding high-risk areas, which decouples human infection from the underlying disease ecology, so this is frequently not the case.

Nevertheless, in California, the distribution of infected ticks was a reliable indicator of where people get sick.

Studies conducted in the eastern United States, in contrast, show that ecology and epidemiology are not closely related.

Since Lyme disease is relatively uncommon in the Golden State, MacDonald hypothesizes that there may be a lack of public and medical awareness of the disease, its risk factors, and its symptoms.

While the role of birds is less clear, scientists think they don't significantly contribute to the prevalence of Lyme disease in North American tick populations.

Also Read: Chronic Lyme Disease? Cancer Meds Could Battle it

Climate Change Indicators

One of many significant factors that affect the transmission, prevalence, and incidence of Lyme disease is the climate, as per EPA.

Changes in the host species' populations (especially those of deer), which have an impact on the size of the tick population, are another factor that influences the number of Lyme disease cases.

The prevalence and infection rates of white-footed mice and a few other hosts influence the proportion of infected ticks.

The populations and habitats of host species can be impacted by changes in the climate and other ecosystem disturbances.

Changes in the proximity of human populations to ticks and other hosts increased awareness of Lyme disease, and modified behaviors, such as spending less time outdoors, taking precautions against being bitten, and checking more carefully for ticks, are all factors that can affect human exposure to infected ticks.

An indicator looks at the prevalence of Lyme disease, which represents the frequency of new cases occurring in a specific location and time frame.

The number of cases per 100,000 people per year is the usual unit of measurement for incidence.

The CDC provided annual rates and totals for Lyme disease for each state.

State and local health departments tracked confirmed Lyme disease cases that were identified by medical professionals and reported these cases to the National Notifiable Diseases Surveillance System, which is where the original data came from.