Anaplasmas

Anaplasma spp
Kingdom	Monera
Sub-kingdom	Bacteria
Phylum	Proteobacteria
Order	Rickettsiales
Family	Ehrlichiaceae
Genus	Anaplasma
Species	Anaplasma marginale and others

Introduction

Rickettsial pathogens inside tick haemolymph cells. Source - Wikimedia Commons

Anaplasma species are rickettsial bacterial pathogens that reside within host erythrocytes.

Anaplasmas cause Anaplasmosis and have worldwide distribution due to their wide range of vectors. Disease is most common in tropical regions.

Lifecycle

Anaplasmas are transmitted by a wide range of tick species and other insects including the Culicoides midge and other biting flies.

Maturation can occur only in tick hosts, flies acting as solely mechanical vectors.

Infectious bacteria reside and replicate within the salivary gland of the vector and are transmitted to mammalian hosts during bloodfeeding.

Infected erythrocytes are disrupted and release bodies which can then invade other erythrocytes. These bodies form vacuoles within the cytoplasmic membranes of the red blood cells and then undergo binary fission to form dense blue-purple round/cube shaped inclusion bodies.

This amplifies infection within the host and increases the likelihood of transmission when insects bloodfeed.

For more information on ticks as disease vectors, se Tick Disease Transmission.

Pathogenesis

Anaplasmosis causes haemolytic anaemia by damaging erythrocytes.

Diseases

Anaplasmosis in domestic and wild ruminants and deer causes profound anaemia, emaciation, haematuria and consequent respiratory and neurological signs.

Anaplasma marginale

Most (70-80%) inclusion bodies are found at or close to the border of the erythrocyte. Infects cattle causing severe anaplasmosis.

Anaplasma centrale

Infects primarily cattle.

Inclusion bodies tend to be central within the red blood cells.

Anaplasma mesaeterum and ovis

Infect mainly sheep and goats.

Usually cause mild disease only.

Inclusion bodies tend to be central within the red blood cells.

References

Animal Health & Production Compendium, Anaplasma marginale, A. centrale, A. mesaenterium, A. ovis datasheets, accessed 04/06/2011 @ http://www.cabi.org/ahpc/

Test Yourself with Anaplasma spp. Flashcards

Anaplasmas Flashcards