MPH 510
ODriscoll
Descriptive Epidemiology Project
Rocky Mountain Spotted Fever

Define the problem (nature, extent, significance, etc.)
 Rocky Mountain spotted fever (RMSF) is a tickborne disease caused by the
bacterium Rickettsia rickettsii. This organism is a cause of potentially fatal human illness
in North and South America, and is transmitted to humans by the bite of infected tick
species. In the United States, these include the American Dog tick (Dermacentor
variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and brown dog tick
(Rhipicephalus sanguineus).
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Describe the agent.
 The causative agent is Rickettsia rickettsii (named after Howard T. Ricketts, the
discoverer of the organism). This organism is an Alphaproteobacteria and member of
the spotted fever group of rickettsial infections.
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Describe the condition (briefly):
 Typical symptoms include: fever, headache, abdominal pain, vomiting, and muscle pain.
A rash may also develop, but is often absent in the first few days, and in some patients,
never develops. Symptoms progress rapidly with respiratory, gastrointestinal, and
neurological manifestations; leading to multisystem organ failure and death. Rocky
Mountain spotted fever can be a severe or even fatal illness if not treated in the first
few days of symptoms. Doxycycline is the first line treatment for adults and children of
all ages, and is most effective if started before the fifth day of symptoms. The initial
diagnosis is made based on clinical signs and symptoms, and medical history, and can
later be confirmed by using specialized laboratory tests (CDC, 2013). RMSF has the
highest mortality of any tick-borne illness in the United States (up to 30%).

Examine sources for data on morbidity and mortality for the selected problem

Summarize these data on the distribution of the selected health problem according to the
following factors, using tables, graphs, or other illustration whenever possible/
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
Host characteristics
1. Age
2. Sex – both female and male; highest among males
3. Nativity – none noted
4. Marital status – none noted
5. Ethnic group – highest among American Indian males.
Environmental attributes
1. Geographical areas – Eastern Arizona, Arkansas, Delaware, Missouri, North
Carolina, Oklahoma, and Tennessee.
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2. Social and economic factors
a. Income – lower income areas with few resources to maintain property
and provide tick control to household dogs.
b. Housing – poor housing maintenance with junk and debris on property
providing harborage areas for the ticks.
3. Occupation – none noted
4. Education – highest incidence rates among lower educated, rural areas.
Temporal variation
1. Secular – Long term trend is showing an increase of cases
2. Cyclic – associated with the life cycle of the tick.
3. Seasonal – illness onset in the summer months with a peak of cases typically in
June and July.
4. Epidemic – not an epidemic, but endemic in parts of the U.S.
Any additional characteristics that contribute to an epidemiologic description of the
disease/health problem:
1. Symptoms:
a) Fever
b) Headache
c) Nausea
d) Vomiting
e) Muscle pain
f) Lack of appetite
g) Conjuctival injection (red eyes)
h) Rash
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Summarize any current hypotheses that have been proposed to explain the observed
distribution
 Demma et al. tested a hypothesis at two similar communities in Eastern Arizona
differing in elevation and temperature range. Community one had a RMSF outbreak two
years earlier and community two did not have any human cases at the time of study.
Their findings showed evidence of exposure to disease in both children and dogs for
both communities.
 The disease in particularly prevalent areas in the United States such as, southern and
south-eastern States, North Carolina, Virginia, Tennessee, Maryland, and Oklahoma is
likely due to the increasing incidence are urban development in previously endemic
areas and an increase in recreations that bring man into contact with the animal hosts.
However, there has been little research into this hypothesis.
 Since RMSF is closely associated with dogs, there is a hypothesis that the disease
increases with an increase in canine population. However, there is little research into
this.
 http://www.youtube.com/watch?v=jdnCdM98oCA
List any principal gaps in knowledge about the distribution of the health problem.
 A study conducted by Paddock, Chirstopher. et al. found that most deaths caused by
RMSF are missed, unreported, or unconfirmed because pathologist have a difficult time
demonstrating rickettsiae in patient tissue. This study suggests that RMSF is more likely
to be more prevalent than the experts think.
Suggest areas for further epidemiological research.
 Research the association between RMSF and animal control laws in areas with a high
prevalence rate. Would strict animal control laws reduce RMSF?
 Research between property standard codes and enforcement in areas with high
incidence rates of RMSF. Does rigorous property maintenance enforcement reduce
harborage areas for the ticks?
 Similarities in culture (environmental issues) between American Indians and areas with
high prevalence of RMSF in Central and South America (Panama, Brazil).
References:
Centers for Disease Control and Prevention. (2013, November). Rocky Mountain Spotted Fever (RMSF).
Retrieved from http://www.cdc.gov/rmsf/index.html
Christopher D. Paddock, Patricia W. Greer, Tara L. Ferebee, Joseph Singleton, Jr., Don B. McKechnie,
Tracee A. Treadwell, John W. Krebs, Matthew J. Clarke, Robert C. Holman, James G. Olson, James E.
Childs, and Sherif R. Zaki (1999). Hidden Mortality Attributable to Rocky Mountain Spotted Fever:
Immunohistochemical Detection of Fatal, Serologically Unconfirmed Disease. The Journal of
Infectious Disease (179.1), 1469-1478.
Demma L., Trager, M., Blau, D., Gordon, R., Johnson, B., Dickson, J., Ethelblah, R., Piontkowski, S.,
Levy, C., Nicholson, W., Duncan, C., Heath, K., Cheek, J., Swerdlow, D., and Mcquistion, J. (2006).
Serologic Evidence for Exposure to Rickettsia rickettsii inEastern Arizona and Recent Emergence of
Rocky Mountain Spotted Fever in This Region. Vector-Borne and Zoonotic Diseases, 6(4), 423-428.