Neglected Tropical Diseases Are on the Rise in Texas

Texas has reported outbreaks or transmission cases of diseases such as Zika virus, Ebola virus, murine typhus, and West Nile virus in recent years, and now, a new study details the factors contributing to these disease outbreaks.

According to the Centers for Disease Control and Prevention (CDC), neglected tropical diseases (NTDs) include bacterial and parasitic diseases that cause illness in more than 1 billion people around the world. Some of these communicable diseases include Dengue fever, leprosy, and rabies. NTDs are more prevalent in tropical and subtropical climates, according to the World Health Organization (WHO), and 149 countries and territories in the world are affected by at least one disease in this group. Most of the places worst affected by NTDs have higher populations living in poverty without proper sanitation. Since its 10th meeting of the Strategic and Technical Advisory Group for Neglected Tropical Diseases, the WHO now lists 20 diseases on its target list of NTDs.

Last year, the CDC published a study on the growing number of cases and geographic spread of typhus group rickettsiosis in Texas, where the number of annual cases more than doubled from 2008 to 2016. While typhus is not a condition listed on the CDC’s or the WHO’s list of NTDs, researchers are exploring how the rise of the disease is part of a growing trend of emerging diseases and NTDs in the state. Peter Hotez, MD, PhD, of Baylor College of Medicine and founding editor of the journal PLOS Neglected Tropical Diseases recently wrote a paper in the journal exploring the modern and globalizing forces in “new Texas” that have been contributing to the increase in major NTDs. These factors include parasitic infections, arbovirus infections, and other neglected viral and bacterial infections.

In 2000, the population of Texas was about 20.8 million people, but according to the new paper, the state’s Department of State Health Services (DSHS) estimates the population to hit 30 million by 2020. This rapid population expansion along with urbanization, human migrations, new transportation patterns, climate change, declining vaccination rates, and other factors have all contributed to the increase in emerging diseases and NTDs such as Chagas disease, leishmaniasis, trichomoniasis, intestinal protozoan infections, cysticercosis, and toxocariasis in Texas, though these illnesses go largely underreported, according to Dr. Hotez. For example, while the DSHS reported only 15 locally-acquired cases and 44 imported cases of Chagas disease from 2013 to 2015, the CDC estimates that there are 37,000 individuals in Texas living with this parasitic infection, which is transmitted by insects and mostly found in rural parts of Latin America with high poverty rates.

Earlier this year, Texas passed House Bill 2055, legislation to mandate active surveillance for NTDs, the first such legislation in the state. “Overall, there is a dearth of information on the true prevalence and incidence of NTDs in Texas. A major reason for this is that information is based on reports to local health departments and the Texas DSHS, whereas most of the NTDs in Texas are seldom diagnosed or diagnosed accurately,” notes Dr. Hotez in the paper, pointing out that trends suggest that the state will see more cases of NTDs in the coming years, emphasizing the need for more surveillance throughout several parts of the state.

However, an interview with Contagion^®, Dr. Hotez said that the new legislation may not move the needle quickly enough in Texas. “No money was appended to the bill, so there’s a recognition that a problem exists but they don’t necessarily share my urgency to do something about this issue,” said Dr. Hotez. “We have a difficult time in the United States and in Texas accepting we have a serious problem with poverty and poverty-related neglected diseases.”