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Rocky Mountain spotted fever in Native Americans
Newsdesk
Rocky Mountain spotted fever in Native Americans A rise in Rocky Mountain spotted fever in Arizona’s Native American population has been heralded by the emergence of a new vector. Roxanne Nelson reports. than 350 000 individuals at risk of infection. “There is no biological factor that predisposes American Indians to RMSF” said Naomi Drexler, an epidemiologist from the Rickettsial Zoonoses Branch, CDC. “If they are exposed to the ticks they can become infected, and one reason for the high exposure are the large populations of dogs in these communities.”
“what is unique about the outbreak in Arizona is that transmission has been linked to a new vector, the brown dog tick” Dogs tend to roam freely and belong more to the community in general, rather than being privately owned. “There is a lack of veterinary care, so they are not being treated for tick infestations”, she Drexler. “We also found ticks nestled in the stucco wall of homes, in crawl spaces, and in other areas of the living environment.” RMSF is a tick-borne zoonotic disease that is thus far confined to the Americas, and caused by infection with Rickettsia rickettsii. Ticks, primarily the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni), serve as the reservoir and the vector for this disease in the USA. Although easily treatable with doxycycline, the disease is still among the most virulent known human infections and carries a high fatality rate if left untreated. But because the emergence of this disease is relatively new to this area, trends of the disease have not been well established. Efforts have been made to educate both tribal residents and treating physicians, but people might not be seeking care soon
www.thelancet.com/infection Vol 15 September 2015
enough. Cost is not generally the issue, since many Native Americans are eligible to receive prepaid health care through medical facilities funded by the Indian Health Service. But a delay in diagnosis and treatment are the two primary factors associated with a fatal outcome. “There isn’t time to wait for test results so treatment has to be presumptive, as soon as it’s suspected”, said Drexler. “The average time from the beginning of symptoms to death is only 8 days.” In the USA, tribal lands are considered sovereign and outside the jurisdiction of state and federal governments. However, Drexler noted that the CDC has been working together with state and tribal health authorities to create effective community-based tick control programmes, which are helping to prevent further spread of the disease. Since the 1920s, when cases first began to be tracked in the USA, the infection has proven to be cyclical, going through periods of waxing and waning for several years at a time. There has been a dramatic increase in incidence overall, rising from 1·9 cases per million people in 2000
For more on the brown dog tick and RMSF see PLoS One 2014; 9: e112368 For more on the RMSF casefatality rate and costs in Arizona see Am J Trop Med Hyg 2015; published online June 1. http:// www.ajtmh.org/content/ early/2015/05/28/ ajtmh.15-0104.long
David Scharf/Science Photo Library
As far as human infections go, Rocky Mountain spotted fever (RMSF) has not posed a global risk or even a large regional epidemic. However, it has become an emerging public health issue in several Native American reservations in the US state of Arizona. But what is unique about the outbreak in Arizona is that transmission has been linked to a new vector, the brown dog tick (Rhipicephalus sanguineus sensu lato), which has not been previously shown to transmit RMSF infection in the USA. From 2002 to 2014, there have been more than 300 cases of RMSF and 20 related deaths in Native Americans. The average annual incidence for 2009–12 was roughly 136 cases per 100 000 people on the three reservations that were the most heavily affected, which was more than 150 times the national average. The case-fatality rate in Arizona is also markedly higher than currently observed elsewhere in the USA, averaging 7% of reported cases compared with less than 1% nationally. Among young Native American children aged between 5 and 9 years, the case-fatality rate was significantly higher (11·5% vs 1·7%) compared with white children. In addition to the human toll, the total cost of medical care, loss of productivity, and death in people infected with RMSF on two Native American reservations in Arizona amounts to about US$13·2 million, according to a study from the Center for Disease Control and Prevention (CDC). CDC also believe their data to be substantially underestimating of the cost of the epidemic. As of 2014, there are now six Native American reservations in Arizona with documented cases in human beings, which puts more
Scanning electron micrograph of a brown dog tick.
1013
Newsdesk
to an all-time high of 8·4 cases per million people in 2008. “There are many that believe the rickettsioses and RMSF or related infec tions are truly increasing worldwide”, explained J Stephen Dumler, Professor of Departments of Pathology and Microbiology and Immunology at the University of Maryland School of Medicine, Baltimore, MD, USA. “The precedent for this is the example of the expansion of Lyme disease as the ticks and tick hosts and reservoirs expand in their geographic distributions, and as human populations increase and expand into previously undisturbed ecological regions that sustained the normal transmission patterns of rickettsiae”, he said. However, cases have been consistently higher in Native American compared with other ethnic groups. From 1990 to 2000, the incidence was slightly higher in Native Americans, but jumped dramatically from 2001 to 2005. During this period, the average annual incidence in Native
Americans was 16·8 per 1 million people, whereas for white, black, and Asian or Pacific Islander people it was 4·2, 2·6, and 0·5 per 1 million, respectively. The name Rocky Mountain spotted fever is a bit of a misnomer, because five states, far removed from the Rocky Mountains, account for more than 60% of cases. North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri are all located in the southeastern part of the USA, in climates more conducive to proliferation of the dermacentor ticks. By contrast, the hot arid climate of Arizona is inhospitable to this type of tick, so the risk of contracting the infection has traditionally been quite rare, with only eight cases reported from 1988 to 2003—most of which were acquired outside the state. So how did R sanguineus suddenly become a new vector for the disease, and turn up in Arizona? The answer to that might lie south of the border. Coinciding with the outbreak on tribal lands in Arizona, RMSF has re-emerged in the Sonora region of Mexico, which shares a border
with Arizona. There the disease is also being transmitted by the bite of the R sanguineus tick, and since early 2000, there have been about 100 cases a year. Similar to Arizona, the infection has disproportionately affected Indigenous populations, with an accompanying high fatality rate. “Going back to the 1940s, R sanguineus was identified in Mexico as a vector for pathogenic spottedfever group rickettsiae”, explained David Walker, Director of the Center for Biodefense and Emerging Infectious Disease at the University of Texas Medical Branch in Galveston, TX, USA. “We’ve only seen R sanguineus as a vector of RMSF in the southwestern United States and northern Mexico”, he said. “This could be due to environmental conditions, a large feral dog population, and other factors we don’t yet know about”. But it remains unclear how the ticks became vectors for the disease in Arizona, he said. “It’s all just pure speculation at this point.”
Roxanne Nelson
Infectious disease surveillance update Legionnaires’ disease in New York City For more on Legionnaires disease in New York see http:// www.nyc.gov/html/doh/html/ diseases/cdlegi.shtml For more on mumps in Ireland see http://www.promedmail. org/direct.php?id=3563027 For more on plague in Colorado see http://www.promedmail. org/direct.php?id=3566831
1014
As of Aug 11, 2015, 12 people have died from Legionnaires’ disease traced to air conditioning systems in New York’s Bronx borough. All those who died were adults with underlying conditions. More than 110 people have been diagnosed with the infection, which is caused by inhaling the legionella bacteria in contaminated water droplets. The city’s health department has ordered testing of all buildings with cooling towers in the borough. The infection does not pass from person to person; however, people in an affected building can be infected from the same source. This is the largest outbreak of Legionnaires’ disease in the city’s history.
Mumps in Ireland A mumps outbreak has been reported for the period from July, 2014, to July, 2015, with twice the number of cases reported compared with the previous year. More than 2000 cases were recorded, mostly from the south region which includes Cork, Kerry, Waterford, and South Tipperary. The highest incidence was recorded in the northwest region. Figures from the Health Protection Surveillance Centre showed some gaps in the uptake of the two-dose measles, mumps, and rubella (MMR) vaccine. In the cases with vaccination status available, a large majority reported having received two doses of the vaccine. The vaccine is least effective against mumps; two doses of the vaccine are 88% effective whereas one dose is 78% effective. Immunity might have
waned over time or was only partial to begin with in some of the cases.
Plague in Colorado, USA A Colorado resident from Boulder tested positive for plague, a disease caused by the bacterium Yersinia pestis. This is the first case in Boulder since 1993. The individual had found a dead chipmunk on their property, and a few days later they started experiencing symptoms including fever, chills, muscle pain, loss of appetite, and confusion. The patient sought medical care when the symptoms began and received antimicrobial treatment. This year, three other Colorado residents have fallen ill from plague, with two dying from the disease.
Ruth Zwizwai
www.thelancet.com/infection Vol 15 September 2015
Rocky Mountain spotted fever in Native Americans A rise in Rocky Mountain spotted fever in Arizona’s Native American population has been heralded by the emergence of a new vector. Roxanne Nelson reports. than 350 000 individuals at risk of infection. “There is no biological factor that predisposes American Indians to RMSF” said Naomi Drexler, an epidemiologist from the Rickettsial Zoonoses Branch, CDC. “If they are exposed to the ticks they can become infected, and one reason for the high exposure are the large populations of dogs in these communities.”
“what is unique about the outbreak in Arizona is that transmission has been linked to a new vector, the brown dog tick” Dogs tend to roam freely and belong more to the community in general, rather than being privately owned. “There is a lack of veterinary care, so they are not being treated for tick infestations”, she Drexler. “We also found ticks nestled in the stucco wall of homes, in crawl spaces, and in other areas of the living environment.” RMSF is a tick-borne zoonotic disease that is thus far confined to the Americas, and caused by infection with Rickettsia rickettsii. Ticks, primarily the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni), serve as the reservoir and the vector for this disease in the USA. Although easily treatable with doxycycline, the disease is still among the most virulent known human infections and carries a high fatality rate if left untreated. But because the emergence of this disease is relatively new to this area, trends of the disease have not been well established. Efforts have been made to educate both tribal residents and treating physicians, but people might not be seeking care soon
www.thelancet.com/infection Vol 15 September 2015
enough. Cost is not generally the issue, since many Native Americans are eligible to receive prepaid health care through medical facilities funded by the Indian Health Service. But a delay in diagnosis and treatment are the two primary factors associated with a fatal outcome. “There isn’t time to wait for test results so treatment has to be presumptive, as soon as it’s suspected”, said Drexler. “The average time from the beginning of symptoms to death is only 8 days.” In the USA, tribal lands are considered sovereign and outside the jurisdiction of state and federal governments. However, Drexler noted that the CDC has been working together with state and tribal health authorities to create effective community-based tick control programmes, which are helping to prevent further spread of the disease. Since the 1920s, when cases first began to be tracked in the USA, the infection has proven to be cyclical, going through periods of waxing and waning for several years at a time. There has been a dramatic increase in incidence overall, rising from 1·9 cases per million people in 2000
For more on the brown dog tick and RMSF see PLoS One 2014; 9: e112368 For more on the RMSF casefatality rate and costs in Arizona see Am J Trop Med Hyg 2015; published online June 1. http:// www.ajtmh.org/content/ early/2015/05/28/ ajtmh.15-0104.long
David Scharf/Science Photo Library
As far as human infections go, Rocky Mountain spotted fever (RMSF) has not posed a global risk or even a large regional epidemic. However, it has become an emerging public health issue in several Native American reservations in the US state of Arizona. But what is unique about the outbreak in Arizona is that transmission has been linked to a new vector, the brown dog tick (Rhipicephalus sanguineus sensu lato), which has not been previously shown to transmit RMSF infection in the USA. From 2002 to 2014, there have been more than 300 cases of RMSF and 20 related deaths in Native Americans. The average annual incidence for 2009–12 was roughly 136 cases per 100 000 people on the three reservations that were the most heavily affected, which was more than 150 times the national average. The case-fatality rate in Arizona is also markedly higher than currently observed elsewhere in the USA, averaging 7% of reported cases compared with less than 1% nationally. Among young Native American children aged between 5 and 9 years, the case-fatality rate was significantly higher (11·5% vs 1·7%) compared with white children. In addition to the human toll, the total cost of medical care, loss of productivity, and death in people infected with RMSF on two Native American reservations in Arizona amounts to about US$13·2 million, according to a study from the Center for Disease Control and Prevention (CDC). CDC also believe their data to be substantially underestimating of the cost of the epidemic. As of 2014, there are now six Native American reservations in Arizona with documented cases in human beings, which puts more
Scanning electron micrograph of a brown dog tick.
1013
Newsdesk
to an all-time high of 8·4 cases per million people in 2008. “There are many that believe the rickettsioses and RMSF or related infec tions are truly increasing worldwide”, explained J Stephen Dumler, Professor of Departments of Pathology and Microbiology and Immunology at the University of Maryland School of Medicine, Baltimore, MD, USA. “The precedent for this is the example of the expansion of Lyme disease as the ticks and tick hosts and reservoirs expand in their geographic distributions, and as human populations increase and expand into previously undisturbed ecological regions that sustained the normal transmission patterns of rickettsiae”, he said. However, cases have been consistently higher in Native American compared with other ethnic groups. From 1990 to 2000, the incidence was slightly higher in Native Americans, but jumped dramatically from 2001 to 2005. During this period, the average annual incidence in Native
Americans was 16·8 per 1 million people, whereas for white, black, and Asian or Pacific Islander people it was 4·2, 2·6, and 0·5 per 1 million, respectively. The name Rocky Mountain spotted fever is a bit of a misnomer, because five states, far removed from the Rocky Mountains, account for more than 60% of cases. North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri are all located in the southeastern part of the USA, in climates more conducive to proliferation of the dermacentor ticks. By contrast, the hot arid climate of Arizona is inhospitable to this type of tick, so the risk of contracting the infection has traditionally been quite rare, with only eight cases reported from 1988 to 2003—most of which were acquired outside the state. So how did R sanguineus suddenly become a new vector for the disease, and turn up in Arizona? The answer to that might lie south of the border. Coinciding with the outbreak on tribal lands in Arizona, RMSF has re-emerged in the Sonora region of Mexico, which shares a border
with Arizona. There the disease is also being transmitted by the bite of the R sanguineus tick, and since early 2000, there have been about 100 cases a year. Similar to Arizona, the infection has disproportionately affected Indigenous populations, with an accompanying high fatality rate. “Going back to the 1940s, R sanguineus was identified in Mexico as a vector for pathogenic spottedfever group rickettsiae”, explained David Walker, Director of the Center for Biodefense and Emerging Infectious Disease at the University of Texas Medical Branch in Galveston, TX, USA. “We’ve only seen R sanguineus as a vector of RMSF in the southwestern United States and northern Mexico”, he said. “This could be due to environmental conditions, a large feral dog population, and other factors we don’t yet know about”. But it remains unclear how the ticks became vectors for the disease in Arizona, he said. “It’s all just pure speculation at this point.”
Roxanne Nelson
Infectious disease surveillance update Legionnaires’ disease in New York City For more on Legionnaires disease in New York see http:// www.nyc.gov/html/doh/html/ diseases/cdlegi.shtml For more on mumps in Ireland see http://www.promedmail. org/direct.php?id=3563027 For more on plague in Colorado see http://www.promedmail. org/direct.php?id=3566831
1014
As of Aug 11, 2015, 12 people have died from Legionnaires’ disease traced to air conditioning systems in New York’s Bronx borough. All those who died were adults with underlying conditions. More than 110 people have been diagnosed with the infection, which is caused by inhaling the legionella bacteria in contaminated water droplets. The city’s health department has ordered testing of all buildings with cooling towers in the borough. The infection does not pass from person to person; however, people in an affected building can be infected from the same source. This is the largest outbreak of Legionnaires’ disease in the city’s history.
Mumps in Ireland A mumps outbreak has been reported for the period from July, 2014, to July, 2015, with twice the number of cases reported compared with the previous year. More than 2000 cases were recorded, mostly from the south region which includes Cork, Kerry, Waterford, and South Tipperary. The highest incidence was recorded in the northwest region. Figures from the Health Protection Surveillance Centre showed some gaps in the uptake of the two-dose measles, mumps, and rubella (MMR) vaccine. In the cases with vaccination status available, a large majority reported having received two doses of the vaccine. The vaccine is least effective against mumps; two doses of the vaccine are 88% effective whereas one dose is 78% effective. Immunity might have
waned over time or was only partial to begin with in some of the cases.
Plague in Colorado, USA A Colorado resident from Boulder tested positive for plague, a disease caused by the bacterium Yersinia pestis. This is the first case in Boulder since 1993. The individual had found a dead chipmunk on their property, and a few days later they started experiencing symptoms including fever, chills, muscle pain, loss of appetite, and confusion. The patient sought medical care when the symptoms began and received antimicrobial treatment. This year, three other Colorado residents have fallen ill from plague, with two dying from the disease.
Ruth Zwizwai
www.thelancet.com/infection Vol 15 September 2015