A changing landscape of infectious disease in southwestern American Indian communities

Despite effective vaccines, pneumococcal disease still threatens health

Theme(s):
Infectious Disease Prevention

In 1978, Dr. Jim Campbell moved to the Navajo Nation to begin work for the Indian Health Service as part of a two-year school loan payback program. What he witnessed upon his arrival took him by surprise.

Meningitis, diarrhea, and other forms of infectious disease normally uncommon in other parts of the United States were taking a considerable toll upon the survival and well-being of Navajo children.

“I saw firsthand this incredible disease burden,” said Dr. Campbell, pictured below, “(and) I decided to stay and work.”

Decades later, Dr. Campbell, now a research study physician for the Johns Hopkins Center for American Indian Health, can safely say that he has seen significant improvements in the health of Navajo children. The introduction of Oral Rehydration Solutions (ORS) and various immunizations – in which the Center has played a major role – have greatly reduced the impact of infectious disease.

“As more kids got immunized against pneumococcal disease, I have seen a big reduction in disease,” said Carol Tso, a registered nurse and member of the Navajo Nation who monitors a large area in the Nation for pneumococcal disease and other deadly pathogens. “Actually, I have seen almost no pneumococcal ear infections in children over the past three years,” she said.

But Tso, Dr. Campbell, and other staff members of the Center’s Active Bacterial Surveillance Program say that there is still much more work to be done.

The surveillance program seeks to monitor rates of Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae on the Navajo Nation and White Mountain Apache reservation. These bacteria can infect areas of the body that are normally free of the germs – such as the lung, blood or fluids and tissues surrounding the brain and spinal cord – and cause potentially lethal medical conditions, such as pneumonia, sepsis, and meningitis.

The program partners with Indian Health Service microbiology laboratories and private facilities to identify cases of invasive bacterial disease and to gather more information on the disease event, patient demographics, vaccination history, hospitalization, and underlying medical conditions. It also collects isolates of the bacteria in order to track the prevalence of different strains and monitor the impact of interventions like vaccines.

Use of the vaccine against Haemophilus influenzae type b (Hib) has resulted in the near elimination of disease caused by this bacterium among Navajo and White Mountain Apache children. And, the Streptococcus pneumoniae vaccine – which provides protection against 13 types or strains of pneumococcus – has reduced the rate of infection by vaccine-type strains by 99% in children and by 69% in adults.

“The dramatic improvements came because we have better weapons and those weapons are immunizations,” Dr. Campbell said.

Still, despite the impact of the vaccines, rates of invasive pneumococcal disease among Navajo and White Mountain children are 3.4 times the Healthy People 2020 Objectives and rates among adults are 4.3 times the 2020 Objectives. Concern also exists as to how much disease caused by types not covered by the vaccine will occur.

Streptococcus pneumoniae bacteria commonly reside in the back of the nose without causing an infection (carriage). Vaccination against pneumococcus prevents carriage by the vaccine types, but non-vaccine type strains fill the void left by the vaccine-type strains. This occurrence, known as serotype replacement, poses a challenge to vaccination efforts.

While the evidence suggests that the vaccine has greatly lowered rates of disease without any substantial increase in non-vaccine type disease on either the Navajo Nation or White Mountain Apache Reservation, serotype replacement is important to monitor. Data are critical to knowing whether a prevention program is working and to guiding the development of treatment and prevention programs.

Strep pneumo [pneumococcus] is still a pretty big issue for American Indian people,” said Tso. “The available vaccines only work against a fraction of the more than 90 serotypes causing us to get sick,” she said.

Going forward, the surveillance program will continue to monitor invasive bacterial disease and to identify risk factors for infection, as well as protective factors against infection.

Story by Will Bellamy

Photos by Ed Cunicelli