The Rickettsial Diseases of Mexico

Although the “rickettsiosis” reported in Michoacan could represent Rocky Mountain spotted fever, the extent and location of this outbreak suggests a diagnosis of Endemic typhus. In the following graph, I’ve compared the incidence of these two diseases in Mexico.

In fact, six Rickettsiae (including Coxiella burnetii, a related taxon) are reported in Mexico. The following summary is abstracted from Gideon www.GideonOnline.com and references 1-3. (primary references available on request)

Rickettsia felis:
Rickettsia felis infection was first identified in the Yucatan in 1996, where the organism has subsequently been identified in both humans and fleas.
- Infected fleas have also been recovered from flying squirrels in Mexico.
- Four cases were documented in the Yucatan to 2006.
- Eight cases (3 fatal) of “spotted fevers” were reported in the Yucatan during 2006 to 2007.
Prevalence surveys:
20% of Ctenocephalides felis fleas in Yucatan (2002 publication)
Seroprevalence surveys:
5% of healthy persons in Yucatan (1999)

Epidemic typhus:
– 7,353 fatal cases of epidemic typhus were reported during 1893 to 1907.
– 1,220 cases (707 fatal) were reported during 1939 to 1943.
– The average incidence during 1959 to 1961 was 146 cases per year.
– 64 cases (14 fatal) were reported during 1960 to 1963.
– A total of three outbreaks were reported during the 1980′s – two in Chiapas and one in Mexico State.
Prevalence surveys:
0% of body lice from prisoners and homeless persons in Mexico City (2009 publication)
Notable outbreaks:
1951 – An outbreak (737 fatal cases) was reported.
1966 – An outbreak (10 cases, 0 fatal) was reported in Zoyatlan de Juarez.
1966 to 1967 – An outbreak (18 cases, 3 fatal) was reported in Minas Viejas (Mexico State).
1967 – An outbreak (40 cases, 1 fatal) in Atlacomulco, Mexico State, originated from a patient with Brill-Zinsser disease.
1983 – An outbreak (102 cases, 0 fatal) was reported in Mexico State

Endemic typhus:
Endemic typhus is reported in Guerrero, Hidalgo, Jalisco, Mexico, Michoacan, Nayarit, Nuevo Leon, Oaxaca, Puebla, Quertaro, Tamaulipas, Yucatan and Zacatecas States.
Seroprevalence surveys:
14% to 17% of blood donors in Mexico City (2004 publication)

Rocky Mountain spotted fever
In Mexico, this disease is known as fiebre machada.
– During 1930 to 1950, cases were reported from Coahuila, Durango, San Luis Potosi, Sinaloa and Sonora.
– Rocky Mountain spotted fever has been identified in the Yucatan since 2005.
– Cases continue to occur in Sonora as of 2010
– Mexico’s first fatal case was reported in the southwestern region in 2004.
– 52 cases were reported in Baja California during February to July, 2009.
Prevalence surveys:
40% of patients suspected of having dengue (Yucatan and Jalisco, 1993)
Seroprevalence surveys:
5.6% of persons in rural Yucatan are seropositive toward spotted fever-group rickettsiae (possibly the R. akari group, 1999 publication)
Vectors:
The local vector is Rhipicephalus sanguineus.
- Spotted fever-group rickettsiae have also been isolated from Amblyomma cajennense in Veracruz.
- Amblyomma imitator has been identified as a potential vector in Nueva Leon.
Notable outbreaks:
2009 – An outbreak (4 fatal cases) was reported in Baja California.

Rickettsialpox
– Two cases of rickettsialpox were documented in Yucatan in 2008.
– Evidence of canine infection has been reported in Yucatan (2009 publication)

Q fever:
Seroprevalence surveys:
2% of humans, 2% of cattle and 6% of goats and sheep (1952)
1.46% of cows (1950)
28% of the dairy cattle, 10% of beef cattle, 35% of goats and 40% of sheep (Nueva Leon, 2002 publication)

References:
1. Berger S. Infectious Diseases of Mexico, 2011. 446 pp, 128 graphs, 1,655 references. Gideon e-books, http://www.gideononline.com/ebooks/country/infectious-diseases-of-mexico/
2. Berger S. Endemic Typhus: Global Status, 2011. 65 pp, 90 graphs, 83 references. Gideon e-books,
http://www.gideononline.com/ebooks/disease/epidemic-typhus-global-status/
3. Graph tutorial at: http://www.GIDEONonline.com/wp/wp-content/uploads/Gideon-Graphs.pps

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