Ehrlichiosis S Ehrlichiosis is a group of diseases, usually named according to the host l species and the type of white blood cell most often infected. i d Ehrlichiosis e Canine Monocytic Ehrlichiosis, Canine Rickettsiosis, Canine Hemorrhagic Fever, Tropical Canine Pancytopenia, Tracker Dog Disease, Canine Tick Typhus, Nairobi Bleeding Disorder, Canine Granulocytic Ehrlichiosis, Equine Monocytic Ehrlichiosis, Potomac Horse Fever, Equine 1 Granulocytic Ehrlichiosis, Tick-borne Fever, Human Monocytic Ehrlichiosis, Human Granulocytic Ehrlichiosis, Sennetsu Fever, Glandular Fever S In today’s presentation we will cover information regarding the l Overview organisms that cause ehrlichiosis and their epidemiology. We will also i • Organism talk about the history of the disease, how it is transmitted, species that it d • History affects (including humans), and clinical and necropsy signs observed. e • Epidemiology Finally, we will address prevention and control measures, as well as • Transmission actions to take if ehrlichiosis is suspected. • Disease in Humans 2 • Disease in Animals • Prevention and Control Center for Food Security and Public Health, Iowa State University, 2013 S l i d e THE ORGANISM 3 S Ehrlichiosis is a broad term used for a group of diseases that are usually l The Organism(s) named according to the host species and the type of white blood cell i • Coccobacilli infected. The organisms that cause ehrlichiosis are small pleomorphic d – Small, pleomorphic gram-negative obligate intracellular coccobacilli. There are three – Gram negative intracytoplasmic forms: initial body, elementary body, morula (a e – Obligate intracellular vacuole-bound cluster of organisms that appears as a basophilic • Three intracytoplasmic forms – Initial body inclusion in monocytes or granulocytes). In blood smears, the morula is 4 – Elementary body – Morula diagnostic for ehrlichiosis. Center for Food Security and Public Health, Iowa State University, 2013 [Photo: Morulae detected in a monocyte on a peripheral blood smear, associated with E. chaffeensis infection. Source: CDC] S The zoonotic species are Ehrlichia chaffeensis, Ehrlichia ewingii, l Zoonotic Species Anaplasma phagocytophilum, Neorickettsia sennetsu. Ehrlichia canis i • Ehrlichia chaffeensis may also be zoonotic but this remains to be confirmed. An organism that d • Ehrlichia ewingii appears to be a strain of E. canis was recently isolated from a chronically e • Anaplasma phagocytophilum infected, asymptomatic human in Venezuela. The same strain was • Neorickettsia sennetsu isolated from local dogs. • Ehrlichia canis (possibly) 5 Center for Food Security and Public Health, Iowa State University, 2013 Center for Food Security and Public Health 2013 1 Ehrlichiosis S Ehrlichia not currently thought to be zoonotic include Ehrlichia bovis, l Non-zoonotic Species which causes bovine petechial fever in cattle in the Middle East, Africa i • Ehrlichia bovis and Sri Lanka; Ehrlichia muris, found in rodents in Japan and not d • Ehrlichia muris currently associated with any disease; Ehrlichia ondiri, found in cattle e • Ehrlichia ondiri and wild ruminants in Africa; Ehrlichia ovina, isolated from sheep in the • Ehrlichia ovina Middle East; Ehrlichia ruminantium (formerly Cowdria ruminantium), • Ehrlichia ruminantium which causes heartwater in ruminants. This organism has also been 6 • Anaplasma platys • Neorickettsia risticii found in dogs with symptoms suggestive of canine ehrlichiosis; Anaplasma platys (formerly Ehrlichia platys), which causes cyclic Center for Food Security and Public Health, Iowa State University, 2013 canine thrombocytopenia. It has been found in dogs in the United States, Taiwan, Greece and Israel; Neorickettsia risticii, which causes Potomac horse fever/ equine monocytic ehrlichiosis in the U.S. This organism has also been identified in dogs with the symptoms of ehrlichiosis. S Canine monocytic ehrlichiosis is caused by Ehrlichia canis and, l Ehrlichial Diseases occasionally, E. chaffeensis. Canine granulocytic ehrlichiosis is caused Disease Causative Agent by Anaplasma phagocytophilum and Ehrlichia ewingii. Equine i Canine monocytic ehrlichiosis Ehrlichia canis Ehrlichia chaffeensis monocytic ehrlichiosis/Potomac horse fever is caused by Neorickettsia d Canine granulocytic ehrlichiosis Anaplasma phagocytophilum Ehrlichia ewingii risticii (formerly Ehrlichia risticii). Equine granulocytic ehrlichiosis is e Equine monocytic ehrlichiosis Neorickettsia risticii (Potomac horse fever) Equine granulocytic ehrlichiosis Anaplasma phagocytophilum caused by Anaplasma phagocytophilum. Tick-borne fever, a disease of Tick-borne fever Anaplasma phagocytophilum Human monocytic ehrlichiosis Ehrlichia chaffeensis ruminants, is caused by Anaplasma phagocytophilum. Human monocytic 7 Ehrlichia ewingii Human granulocytic ehrlichiosis Anaplasma phagocytophilum ehrlichiosis is caused by Ehrlichia chaffeensis and E. ewingii. Human Sennetsu fever Neorickettsia sennetsu granulocytic ehrlichiosis is caused by Anaplasma phagocytophilum. Center for Food Security and Public Health, Iowa State University, 2013 Sennetsu fever is caused by Neorickettsia sennetsu (formerly Ehrlichia sennetsu). S l i d e HISTORY 8 S Human infections with Neorickettsia sennetsu have been reported since l History the 1950s, but Ehrlichia chaffeensis, E. ewingii and Anaplasma i • 1950s phagocytophilum were first found to infect humans in the 1980s; the – Human infections with Neorickettsia prevalence and full of extent of the disease are, in many cases, still d sennetsu reported e • 1980s unknown. E. canis has, to date, only been isolated from one – New species recognized in humans asymptomatically infected human. • Ehrlichia chaffeensis 9 • E. ewingii • Anaplasma phagocytophilum Center for Food Security and Public Health, Iowa State University, 2013 Center for Food Security and Public Health 2013 2 Ehrlichiosis S l i d e EPIDEMIOLOGY 1 0 S E. chaffeensis, E. canis and Anaplasma phagocytophilum are found l Geographic Distribution worldwide. E. ewingii has been described, to date, only in the i • Worldwide southeastern and south central United States. E. sennetsu has been – E. chaffeensis, E. canis, reported mainly in Japan and Malaysia, but may exist in other parts of d A. phagocytophilum e • Southeast/south central U.S. Asia. In some cases, disease syndromes are not reported from the – E. ewingii organism’s entire geographic range. Although Anaplasma • Japan, Malaysia 1 phagocytophilum is found worldwide, tickborne fever (or a similar – E. sennetsu syndrome) has been reported only in ruminants in Europe, India and 1 South Africa. Center for Food Security and Public Health, Iowa State University, 2013 S In dogs, ehrlichiosis is reported throughout the year, due to the l Seasonality prolonged clinical course and the ability of its tick vector (Rhipicephalus i • Dogs appendiculatus) to survive indoors. In the U.S., equine granulocytic d – No seasonal variation ehrlichiosis is most common in California, with sporadic cases reported – Disease occurs e throughout the year in other states. Most cases are seen in late fall, winter and spring. In • Horses cattle, tick-borne fever usually occurs as a spring and early summer – Late fall, winter, spring epidemic when dairy cattle are turned out to pasture. In sheep, symptoms 1 – California are usually seen in young lambs born in tick-infested areas and older 2 • Cattle (tick-borne fever) – Spring, early summer sheep introduced to such areas.[Photos: (Top) Dog. Source: Marilyn Center for Food Security and Public Health, Iowa State University, 2013 Peddle/Wikimedia Commons; (Middle) Horse. Source: Steve Hillebrand/US Fish and Wildlife Service; (Bottom) Cattle in field. Source: USDA NRCS] S Data Table for Number of Annual Ehrlichiosis Cases, 1994 – 2010 l Incidence in Humans The graph displays the number of human cases of ehrlichiosis cases i reported to CDC annually from 1994 through 2010. Cases of ehrlichiosis d have increased steadily from 200 cases in 2000, when the disease e became nationally notifiable, to 961 cases in 2008. Cases decreased significantly in 2010 from 944 reported in 2009 to 740 reported in 2010. 1 [Source: Centers for Disease Control and Prevention at http://www.cdc.gov/ehrlichiosis/stats/] 3 Center for Food Security and Public Health, Iowa State University, 2013 S l i d e TRANSMISSION 1 4 Center for Food Security and Public Health 2013 3 Ehrlichiosis S Ehrlichiae are transmitted by ticks in the family Ixodidae. Ehrlichia l Transmission canis is transmitted by the brown dog-tick Rhipicephalus sanguineus. i • Ticks (family Ixodidae) Recently it was also shown to be experimentally transmitted by – Ehrlichia canis • Rhipicephalus sanguineus Dermacentor variabilis, the American dog tick. E. chaffeensis is mainly d – Brown dog tick • Dermacentor variablis transmitted by Amblyomma americanum, the Lone Star tick. e – American dog tick – E. chaffeensis Amblyomma americanum is also thought to be the primary vector for E. • Amblyomma americanum – Lone Star tick ewingii. In addition, evidence of infection has been found in 1 – E. ewingii • Amblyomma americanum Dermacentor variabilis and Rhipicephalus sanguineus. 5 • Dermacentor variablis • Rhipicephalus sanguineus Center for Food Security and Public Health, Iowa State University, 2013 [Photo: (Top) Rhipicephalus sanguineus, brown dog tick; (Bottom) Amblyomma americanum, the Lone Star tick. Source: CDC Public Health Image Library] S Anaplasma phagocytophilum is transmitted by species of Ixodes. In the l Transmission