COMBINED HUMAN AND PORCINE MASS CHEMOTHERAPY FOR THE CONTROL
OF T. SOLIUM
H. H. GARCIA,* A. E. GONZALEZ, R. H. GILMAN, L. H. MOULTON, M. VERASTEGUI, S. RODRIGUEZ, C. GAVIDIA,
V. C. W. TSANG, AND THE CYSTICERCOSIS WORKING GROUP IN PERU
Department of Microbiology, Universidad Peruana Cayetano Heredia, San Martin de Porras, Lima, Peru; Cysticercosis Unit, Instituto
de Ciencias Neurologicas, Barrios Altos, Lima, Peru; Department of International Health, Johns Hopkins University Bloomberg
School of Public Health, Baltimore, Maryland; School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos,
Salamanca de Monterrico, Lima, Peru; A.B.PRISMA, San Miguel, Lima, Peru; Parasitic Diseases Branch, Centers for Disease
Control, Atlanta, Georgia
Abstract. A combined (human and porcine) mass chemotherapy program was tested in a controlled design in 12
village hamlets in the Peruvian highlands. A single dose of 5 mg of praziquantel was given to eliminate intestinal taeniasis
in humans, and two rounds of oxfendazole (30 mg/kg) were administered to all pigs. The total population in the study
villages was 5,658 resident individuals, and the porcine population at the beginning of the study was 716 pigs. Human
treatment coverage was 75%, ranging from 69% to 80%. There were only a few refusals of owners for porcine treatment
of their animals. The effect of the intervention was measured by comparing incidence rates (seroconversion in pigs who
were seronegative 4 months before) in treatment versus control villages, before and up to 18 months after treatment.
There was a clear effect in decreasing prevalence (odds ratio, 0.51; P < 0.001) and incidence (odds ratio, 0.39; P 0.013)
in the treatment area after the intervention, which did not leave to extinction of the parasite but stabilized in slightly
decreased rates persisting along the follow-up period. Mass chemotherapy was effective in decreasing infection pressure
in this hyperendemic area. However, the magnitude of the effect was small and did not attain the goal of eliminating
transmission.
INTRODUCTION
Taenia solium taeniasis/cysticercosis is endemic in most de-
veloping countries.
1,2
The adult tapeworm (taeniasis) occurs
only in humans and carries mild clinical manifestations or
none at all. However, it is the source of infection with the
larval form (cysticercosis), which affects humans and pigs.
Human cysticercosis is a major cause of seizures and other
neurologic symptoms in disease-endemic zones,
3–6
and por-
cine cysticercosis carries important economical losses caused
by damaged pork.
1,7
The life cycle is sustained because of
domestic pig raising and lack of sanitary conditions, which
permit free-ranging pigs access to contaminated feces from a
tapeworm carrier.
T. solium infection has been included into a short list of
eradicable parasitic diseases,
8,9
on the basis of several factors:
1) evidence of eradication in defined geographic areas (Eu-
rope, North America) through improvements in sanitation
and living conditions; 2) a single (human) definitive host,
source of cysticercosis infection; 3) domestic animals perpetu-
ating the cycle, wild cycle not important in transmission; and
4) availability of control measures, including massive anthel-
minthic treatment of humans in endemic areas.
10,11
Currently,
control of porcine cysticercosis is based on inspection and
condemnation of infected pig carcasses.
12
Less than 10% of
Peruvian pigs, however, are registered, and 55% are illegally
slaughtered.
7
In abattoirs where control and confiscation are
not carried out, rates of infection among pigs may be as high
as 30%.
7
Thus, control measures to prevent human consump-
tion are impractical and currently inadequate in endemic ar-
eas.
A series of specific control measures, in addition to abattoir
inspection, must be instituted to prevent human and swine
cysticercosis.
13
Several groups have attempted to actively
control T. solium in endemic areas by applying mass human
chemotherapy,
14–18
pig immunization,
19–22
health educa-
tion,
23
and other interventions.
24
However, elimination of
taeniasis/cysticercosis has not been achieved to date, the ef-
fect of interventions has always been partial, and no conclu-
sive data on sustainability exist. From all attempted interven-
tions, mass chemotherapy has been consistently shown to de-
crease prevalence of infection in Ecuador,
14
Mexico,
17
and
Guatemala,
18
and thus seemed to be the most promising tool.
By adding the use of oxfendazole, recently described to be
effective for porcine cysticercosis,
25
we performed, in an en-
demic area of Peru, the first combined human and porcine
mass chemotherapy trial to control the transmission of T.
solium.
MATERIALS AND METHODS
Overall study design. Cohort study to evaluate the effect of
a combined (human and porcine chemotherapy) intervention
for the control of T. solium comparing the prevalence and
incidence of porcine cysticercosis in treated versus compari-
son areas. Outcomes were evaluated every 4 months after the
intervention for a total of 20 months.
Study site. The central highland area of Peru was selected
because of shown endemicity
7
and accessibility by road. The
zone is cold and has at least two clearly defined seasons: dry
from June to November and wet from December to May.
Paved access highways are passable during all of the year,
although connecting roads may not be used during the rainy
season. A preliminary trip was performed to select an ad-
equate study area on the basis of accessibility and their will-
ingness to cooperate in a longitudinal project on the control
of porcine cysticercosis. In this trip, several villages located
less than 50 miles from Huancayo (population 300,000), the
main city in the Department, were visited and inspected. The
selection of communities near Huancayo was made because
of the convenience of a city-based location for specimen han-
dling, centrifugation, and storage.
* Address correspondence to Hector H. Garcia, Department of Mi-
crobiology, Universidad Peruana Cayetano Heredia. Av. H. Delgado
430, SMP, Lima 31, Peru. E-mail: hgarcia@jhsph.edu
Am. J. Trop. Med. Hyg., 74(5), 2006, pp. 850–855
Copyright © 2006 by The American Society of Tropical Medicine and Hygiene
850