Date: Wed 29 Nov 2017 06:38
Source: Science Nordic [edited]
Norway is home to roughly 5 million people and nearly a million sheep. Sheep, which wander freely in the Norwegian forests and mountains in the summer, can be infected by _Anaplasma phagocytophilum_, a bacterium carried by ticks that can also infect humans and cattle.
Medical researchers have previously described the tick-borne infection caused by _A. phagocytophilum_ as the most widespread tick-borne infection in animals in Europe.
But its prevalence in Norway in humans is so poorly known that the discovery of a case of anaplasmosis in a man at Stavanger University Hospital merited a just-published report in the December 2017 issue of Lancet Infectious Disease . "This was the 1st confirmed case we have seen in Rogaland County," said Ase Berg, chief attending physician at Stavanger University Hospital, where the infected man was seen.
Although this was the 1st report of the disease, Berg and others say that it is likely that many other people in the county have been infected. In late May 2016, a man came to Stavanger University Hospital reporting that he had experienced recurring attacks of high fever, headaches and achy muscles over the previous 10 days. The doctors who saw him were initially puzzled. They tested him for different blood diseases and cancers and for a number of infectious diseases, such as HIV and hepatitis, but without finding anything. But then the doctors learned that the man often spent time camping in the woods. These are areas where ticks often infect sheep with _A. phagocytophilum_. The doctors took a sample from his bone marrow and found the bacteria there. The bacterium that causes anaplasmosis can be found by looking at white blood cells under a light microscope, as is shown in this picture. [Photo available at source URL.]
"Between 300,000 and 400,000 lambs are infected here every year," said Professor Snorre Stuen at the Norwegian University of Life Sciences (NMBU), who has studied anaplasmosis for 30 years. In sheep, anaplasmosis infection is called "sjodogg", which translates as tick-borne fever. It has been known for hundreds of years in Norway. The infection can make sheep very ill. Many animals die or are permanently weakened, primarily because the bacterium makes them vulnerable to other infections.
Although there are few reported cases in Norway, it is also known that ticks can transfer _A. phagocytophilum_ to people. The 1st case of anaplasmosis in humans was described in the United States in 1994 by the Norwegian researcher Johan Bakken, who is currently working at the University of Minnesota. It was 1st reported in a human in Europe in 1997. Since that time, more than 15 000 cases of anaplasmosis have been detected in the United States. The American experience means that we know a bit about the course of the disease in humans.
Like the more well-known Lyme disease, anaplasmosis mostly infects people only when the ticks have been attached to their human hosts for more than a day. Symptoms develop 7 to 10 days after the bite and are reminiscent of the flu, with fever, headache and muscle aches. In many cases, the disease clears up by itself, without the infected individual having any serious or lasting ailments. Bakken says the disease is so mild in many people that they think they have a summer cold. "I would estimate that maybe 2 out of 100 have strong enough symptoms that they go to the doctor," he said of his experience in the Midwestern United States.
However, the disease is not completely benign. In just under one of 100 cases reported, the disease is fatal. "As a rule, it's not anaplasmosis itself that kills people, but that the disease makes people more vulnerable to other infections," says Jens Vikse at Stavanger University Hospital.
Nevertheless, people are not routinely tested for anaplasmosis in Norway. The mildness of the symptoms means that few people go to the doctor, even if they have had a fever for several days. Both of these factors mean that health officials don't actually know how prevalent the disease is in Norway. Several surveys in different Norwegian counties found between 14 and 16 percent of those tested had antibodies to the disease, which suggests it is not uncommon.
Ase Berg at Stavanger University Hospital thinks it would be good to test people who work in the woods, as well as people who participate in the sport of orienteering, which involves running through areas that might have a lot of ticks. The researchers believe that it is important for both healthcare professionals and people to be aware that humans can be infected with this bacterium in areas with ticks. If the disease is detected, it can be treated with antibiotics.
But don't worry: The disease does not appear to be chronic, like Lyme disease. So if you are concerned that you might have had it in the past, you don't need to worry that you will have ongoing problems or that you will get it again. [Byline: Nancy Bazilchuk]
[1. Vikse J, Klos J, Berg A. A travelling camper with a spiking fever, headache, myalgia, hepatitis, and intracellular inclusions, The Lancet Infectious Diseases 2017; 17 (12):1318. DOI:
[_Anaplasma phagocytophilum_, the causative agent of anaplasmosis (also known as human granulocytic anaplasmosis or HGA), is transmitted to humans in northeastern United States by the same tick (_Ixodes scapularis_ in the northeastern and upper central U.S., _Ixodes pacificus_ in California, _Ixodes ricinus_ in Europe, and _Ixodes persulcatus_ in Europe and Asia). _Ixodes_ also transmit _Borrelia burgdorferi_, the causative agent of Lyme disease and _Babesia microti_, the causative agent of babesiosis, as well as Powassan virus the cause of meningoencephalitis. Typically, the nymph stage of the tick, which is about the size of a poppy seed, transmits these diseases. For a picture of the nymph, see <http://www.cdc.gov/parasites/babesiosis/
>. Patients may be concurrently co-infected by these pathogens.
Some individuals infected with _A. phagocytophilum_ do not become ill or experience only very mild symptoms and do not seek medical treatment. The symptoms tend to be most severe in aged or immunosuppressed people. In infected persons who are symptomatic with anaplasmosis, illness onset occurs 5-21 days after a bite from an infected tick. Initial presentation typically includes sudden onset of fever, headache, malaise, and myalgia, often accompanied by thrombocytopenia, leukopenia, and elevated liver transaminases. Approximately 5 to 7 percent of patients require intensive care, and the disease can be fatal. Severe infections can include prolonged fever, shock, confusion, seizures, pneumonitis, renal failure, hemorrhages, and death.
Because _A. phagocytophilum_ are found in the blood stream, infected blood can serve as a vehicle for person-to-person transmission (Centers for Disease Control and Prevention. _Anaplasma phagocytophilum_ Transmitted Through Blood Transfusion -- Minnesota, 2007. MMWR 2008; 57(42): 1145-8. October 2008 [date cited] Available from <http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5742a1.htm
Treatment with doxycycline 100 mg twice daily orally or intravenously for 10 days for all symptomatic patients suspected of having anaplasmosis is recommended for a minimal total course of 10 days. This treatment regimen should be adequate therapy for patients with anaplasmosis alone and for patients who are co-infected with Lyme disease, but is not effective therapy for patients who are co-infected with _B. microti_.
Rogaland, a coastal county located in southwestern Norway with fjords, beaches, and islands, is the center of the Norwegian petroleum industry (<https://en.wikipedia.org/wiki/Rogaland
>). Stavanger, where the patient described in the news report above was hospitalized, is the 3rd-largest urban zone in Norway and the administrative center of Rogaland county.
A map of Rogaland County can be found at
[_Anaplasma phagocytophilum_ has for decades been known to cause the disease tick-borne fever (TBF) in domestic ruminants in _Ixodes ricinus_-infested areas in northern Europe. In recent years, the bacterium has been found associated with Ixodes-tick species more or less worldwide on the northern hemisphere. It has a broad host range, on top of humans; in several mammalian species severe disease may be observed. Fatal cases in animals have been, so far, reported in sheep, cattle, horses, reindeer, roe deer, moose and dogs.
The main disease problems associated with TBF in ruminants are seen in young animals, and individuals purchased from tick-free areas and placed on tick-infested pastures for the 1st time. The most characteristic symptoms in domestic ruminants are high fever, anorexia, dullness, and sudden drop in milk yield. The fever reaction may vary according to the age of the animals, the variant of _A. phagocytophilum_ involved, the host species and immunological status of the host. Abortion in ewes, reduced fertility in rams and reduced weight gain in infected lambs have been observed. For a review addressing _A. phagocytophilum_ in sheep. See ref 1.
1. Stuen S (2016) Tick-Borne Fever (Anaplasma phagocytophilum Infection) in Sheep - A Review. J Vet Med Res 3(5): 1062. - ProMED Mod.AS]
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