Rats and other pests pose significant problems for urban areas in the US.
The people of Los Angeles “smell a rat.”
No, not literally—although this too can be troubling, of course—but figuratively. As in, something is just not right. What has the normally laid-back Southern Californians so unsettled? An ongoing outbreak of typhus.
According to a February 18, 2019, report in the Los Angeles Times, there were 19 cases of the age-old disease among the city’s homeless population, centered in the downtown area, late last year. However, as troubling as this outbreak has been, the numbers suggest it may, in fact, be part of a growing trend. According to state health data cited by the Times, there were 167 cases of typhus in California in 2018, compared with just 13 in 2008. In all, 95% of those infected last year resided in Los Angeles and Orange counties.
“Rodents are the [primary] reservoir for typhus, but opossums and domestic pets can also play a role with bringing infected fleas into the living environment,” said Kristy Murray, DVM, PhD, professor of pediatric tropical medicine and molecular virology at Baylor College of Medicine and director of Texas Children’s Hospital Center for Human Immunobiology, in explaining the challenges facing Los Angeles and other larger cities across the US. Dr. Murray and her team have published several reports on typhus outbreaks, include one in the December 2017 issue of Emerging Infectious Diseases, which described 18 confirmed cases among children in Houston.
“These outbreaks have become much more common over the past decade,” she told Contagion®. “We have witnessed incredible emergence here in Texas similar to what is being seen in California. Before 2007, we had no reported cases of typhus in the Houston area. All typhus transmission was confined to the southern part of the state. In 2003, only 22 cases were reported state-wide, compared to over 700 reported cases a year ago. Now in the summers, we see numerous cases hospitalized here in Houston. In children, we see around 1 out of every 5 cases require intensive care.”
In this most recent outbreak in Los Angeles, many of the cases have been linked with the “Skid Row” area of downtown, which has long been home to a large homeless community. On February 3, 2019, the Daily Wire reported that city officials were taking steps to mitigate the outbreak by increasing trash collection services in the downtown area and ramping up pest control measures. However, Dr. Murray notes that such steps, although important, don’t always have an immediate effect.
“Similar to Houston, LA is a very densely populated urban city, which translates to a very large population at risk for disease, both homeless and non-homeless,” she said. “In Houston, we have also seen a high prevalence of antibodies to typhus in our homeless, supporting a higher risk of transmission to this vulnerable population. Targeted public health measures are critical to interrupt transmission. [But] oftentimes this can be difficult to do. Rodent control in domestic settings is important, as well as flea control on pets. Keeping environments sanitary to prevent infestation is also helpful. Awareness and flea prevention is critical.”
Indeed, this is hardly the first typhus-related challenge to strike the Los Angeles area. Joseph Wakoli Wekesa, PhD, operations manager with Coachella Valley Mosquito and Vector Control District in Indio, California, and colleagues chronicled a much smaller outbreak that occurred in 2015 in the April 2018 issue of PLOS Neglected Tropical Diseases. He told Contagion® that the region has a long history of typhus and, until the early 1990s, both Los Angeles and Orange counties received block grants from the US Centers for Disease Control and Prevention to fund rodent population control efforts. As the grants stopped, such efforts have been reduced over the years due to lack of funds.
“Typhus is found in flea feces, and there have been increases in the area of the opossum and feral cat populations,” Dr. Wekesa said. “Those animals have fleas. Until there are efforts to control the populations of these feral animals from a public health point of view, we are going to see more cases of typhus.”