Macroparasites are parasites that are large enough to be seen with the naked eye, in contrast to microparasite

Microparasite

A microparasite is a parasite that complete a full life cycle within one host and can be transmitted directly to conspecific hosts. They often reproduce within a host's cells and are generally too small to be seen with the naked eye. Most are viruses, bacteria and fungi with a smaller number being...

s. They grow in one host

Host (biology)

In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...

 but reproduce by infective stages outside of this host. These generally include tick

Tick

Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...

s, mite

Mite

Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...

s, nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s, flatworm

Flatworm

The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...

s, etc., and can be either external parasites (ectoparasitic) or internal parasites (endoparasitic). The most abundant macroparasite in humans is the nematode Ascaris lumbricoides

Ascaris lumbricoides

Ascaris lumbricoides is the giant roundworm of humans, belonging to the phylum Nematoda. An ascarid nematode, it is responsible for the disease ascariasis in humans, and it is the largest and most common parasitic worm in humans. One-sixth of the human population is estimated to be infected by this...

. Up to 2000 of these nematodes can be found in a single human . Macroparasitic infection results in around 100,000 deaths a year, mostly in South America, Southeast Asia, and Africa . Macroparasites are also parasitic of many plant species and can be a significant agricultural pest.

Beyond Parasitology

A different distinction between micro- and macroparasites was made by historian William Hardy McNeill in his 1976 book Plagues and Peoples

Plagues and Peoples

Plagues and Peoples is a book on epidemiological history by William Hardy McNeill published in New York City in 1976. It was a critical and popular success, offering a radically new interpretation of the extraordinary impact of infectious disease on cultures as a means of enemy attack...

. Macroparasites are defined by McNeill to be infections used to attack and exploit susceptible neighbouring peoples in a form of epidemiological warfare. The parasitological

Parasitology

Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

 definition of macroparasite is based on parasite life cycles

Biological life cycle

A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...

 rather than the human politics of biological warfare

Biological warfare

Biological warfare is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war...

.