Living organisms, which are considered undesirable, are generally referred to as pests.
Environmental factors (such as weather, geography and soil conditions) which affect pest
populations generally vary from one location to another and changes through time. A com‐
bination of these factors may substantially reduce the pest population in one geographical
area and make it more abundant in another. Pests sometimes outwit their natural enemies
and grow to very high population density. To keep their population in check will necessitate
the manipulation of the population of their natural enemies by man. This is termed biological
control or simply biocontrol. Biocontrol is therefore defined as “any activity of one species
that reduces the adverse effect of another” [ 1 ]. Biocontrol can also be defined as “the study
and uses of parasites, predators and pathogens for the regulation of host (pest) densities”
[ 2 ]. Biological control differs from natural control in that the latter does not involve human
manipulation. The organism that suppresses the pest population is generally referred to as a
biological control agent (BCA).
A parasite is an organism that lives and feeds in or on a host [ 3 ]. Parasites that invade and
live within the host are referred to as endoparasites; meanwhile, those that live on the surface
without invading the host are referred to as ectoparasites. Endoparasites include helminths
and protozoa, and ectoparasites are fleas, ticks, mites, insects and so on. Parasites are a major
cause of disease in man, his livestock and crops, leading to poor yield and economic loss. The
biocontrol of parasites therefore entails the use of BCAs to suppress the population of the
parasites.
This chapter focuses on the biological control of parasites, providing a brief history of bio‐
control; their advantages and disadvantages; types of BCAs including predators, parasites
(parasitoids) and pathogens (fungi, bacteria, viruses and virus‐like particles, protozoa and
nematodes); their effect on the native biodiversity; a few case studies of successful implemen‐
tation of biocontrol; challenges encountered with the implementation of biocontrol strategies
and finally their future perspectives.2. History of biological control
The concept of biological control is not entirely new. The ancient Egyptians were probably
the first to employ biocontrol dating some 4000 years ago, when they observed that cats fed
on rodents, which damaged their crops. This most likely led to the domestication of the house
cat [ 4 ]. However, the first record of biocontrol is from China. As early as the third century, a
nest of the ants Oecophylla smaragdina were sold near Canton (today known as Guangzhou in
China) for use in control of the citrus insect pests such as Tesseratoma papillosa (Lepidoptera).
By 1200 A.D., the usefulness of the ladybird beetles as biological control agents of aphids and
scales had been recognized. Between 1300 and 1799 A.D., the importance of biological control
tools was recognized. Van Leeuwenhoek was probably the first to describe insect parasit‐
ism, which he illustrated in his publication in 1701. In 1726, de Reaumur recognized the first
insect pathogen, a Cordyceps fungus that infects noctuid. The mynah bird, Acridotheres tristis,
was successfully introduced from India to Mauritius by the British and the French for the24 Natural Remedies in the Fight Against Parasites