Nosema apis
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''Nosema apis'' is a
microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or pr ...
n, a small, unicellular
parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
recently reclassified as a fungus that mainly affects
honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
s. It causes nosemosis, also called nosema, which is the most common and widespread of adult honey bee diseases. The dormant stage of ''N. apis'' is a long-lived spore which is resistant to temperature extremes and dehydration, and cannot be killed by freezing the contaminated comb. Nosemosis is a listed disease with the Office International des Epizooties (OIE).


Pathology

''Nosema apis'' is a single-celled parasite of the
western honey bee The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for "bee", and ''mellifera'' is the Latin for "honey-bearing" or "honey carrying" ...
(''Apis mellifera''). The species is of the class
Microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or pr ...
, which were previously thought to be protozoans, but are now classified as fungi or fungi-related. Microsporidia are
intracellular parasites Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a Host (biology), host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative in ...
and they infect the epithelial cells of the midgut. ''N. apis'' has a resistant spore that withstands temperature extremes and dehydration. In 1996, a similar microsporidian parasite of the eastern honey bee (''Apis cerana'') was discovered in Asia, which was named '' Nosema ceranae''. Little is known about the symptoms and the course of the disease. Chinese researchers found ''Nosema ceranae'' in spring 2005 in
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
for the first time, and it has now been seen on western honey bees. The new pathogen was discovered in 2005 in
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
and was observed to have a notably higher virulence than the western version. The disease caused by ''N. ceranae'' in western honey bees in Spain is related to heavier disease patterns deviating from the previously typical findings (unusually heavy intestine injuries in the bees, no
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...
, preferential affliction of older collecting bees). Bees die far away from the dwellings, as when they leave they are too weak to return. This leads to collapse of the bee colony. Within a few years, a strongly increased propagation of ''Nosema'' was observed, and its occurrence was happening all year round due to the higher resistance of ''N. ceranae''. A higher reinfection rate of the bee colonies is assumed, since the pathogen survives longer in the external environment. The two pathogen types cannot be differentiated with usual routine investigations, but can be distinguished only with the assistance of molecular-genetic methods such as
polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
. Spanish researchers regard with alarm the insurgence of ''N. ceranae'' in Spain, which has now replaced ''N. apis''. Because of this newly emergent parasite, the pathogen is assumed to be related to the substantial bee mortality observed in Spain since autumn 2004. They conjectured a similar cause of increased bee colony losses reported in other European countries, such as those experienced in France since end of the 1990s and in Germany in 2002 and 2003. In the samples examined in German laboratories in the winter of 2005/2006, the new pathogen was present in eight of 10 examined bee hives (CVUA Freiburg), with the distribution varying from state to state. The bees with the classical pathogen ''N. apis'' came from
Thuringia Thuringia (; german: Thüringen ), officially the Free State of Thuringia ( ), is a state of central Germany, covering , the sixth smallest of the sixteen German states. It has a population of about 2.1 million. Erfurt is the capital and lar ...
and
Bavaria Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total lan ...
, whereas ''N. ceranae'' prevailed in Baden-Wuerttemberg, Bavaria, and
North Rhine-Westphalia North Rhine-Westphalia (german: Nordrhein-Westfalen, ; li, Noordrien-Wesfale ; nds, Noordrhien-Westfalen; ksh, Noodrhing-Wäßßfaale), commonly shortened to NRW (), is a state (''Land'') in Western Germany. With more than 18 million inha ...
. Cases were also reported from Switzerland (July 2006) and from several regions of
Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
(September 2006) where ''N. ceranae'' was found in bee colonies with increased mortality. German scientistsRitter, Wolfgang, (CVUA Freiburg)
Nosema ceranae. Asiatischer Nosema-Erreger festgestellt. Neu verbreitet oder erst jetzt entdeckt
(translation: Asian nosema pathogene diagnosed. Newly distributed or only lately discovered)?] ADIZ, die Biene, der Imkerfreund (Zeitschrift der Landesverbände) 3/2006, S. 7 (Online auf der Website des Landesverbandes Schleswig-Holsteinischer und Hamburger Imker e. V.).
do not know whether ''N. ceranae'' was already present in Europe and simply had not yet been differentiated from ''N. apis''. The current disease processes possibly are more extreme when a ''Nosema'' affliction occurs because the colonies are already weakened by the ''Varroa'' mite or other factors that make them more susceptible. However, signs indicate the disease process of ''Nosema'' has changed, and the disease arises now all year round. The investigation of 131 bee colonies from Bavaria supports the thesis of a causal participation between bee viruses, which were transferred by
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s (for instance the ''Varroa'' mite), and the periodically arising mass losses of life in the hives. Since only comparatively few of these colonies were afflicted with microsporidians (evidence showed 14.5% of the cases were afflicted with microsporidian spores, with half of the cases by ''N. apis'' and/or ''N. ceranae''), a correlation between microsporidian affliction and virus infection could not be determined. The question of whether the colonies were dying rather from the "new" version of ''Nosema'', which (possibly) possesses a higher pathogenicity, or due to virus diseases connected with ''Varroa'' affliction, is controversially continuing to be discussed internationally among scientists and beekeepers.


Symptoms

The symptoms of ''Nosema'' are relatively nonspecific, which makes it difficult to distinguish from other diseases of the honeybee. It arises mostly in the spring after periods of bad weather, although it may also be a winter disease that is only noticed in the spring when beekeepers first inspect their hives. The female worker bees are most strongly afflicted, less so the drones. The queen bee is rarely infected since afflicted bees rarely participate in feeding the queen. The most notable symptom is
dysentery Dysentery (UK pronunciation: , US: ), historically known as the bloody flux, is a type of gastroenteritis that results in bloody diarrhea. Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation. Complications ...
. This appears as yellow stripes on the outside of the hive and in severe cases, inside the hive. Bees may be unable to fly ("crawling") due to disjointed wings. Further symptoms include increased girth of the abdomen, missing sting reflex, and early replacement of the queen. If the queen is infected, her ovaries degenerate and egg production drops due to atrophy of the oocytes, after which she is likely to be superseded. The disease pattern described by Higes ''et al.''. in Spain for ''N. ceranae'' is slightly different from that of ''N. apis''. The changes in the digestive system were substantially more serious than with ''N. apis'', related to particularly heavy and spacious cell lesions. Conversely, classical symptoms were missing from ''N. ceranae'', such as diarrhea, crawling, large numbers of dead bees in the apiary, etc. Bees tend to die away from the apiary, which causes a reduction in food gathered and can eventually lead to colony collapse. Ritter (CVUA Freiburg) reported symptoms can arise throughout the year from ''N. ceranae'', in contrast to ''N. apis''. In the winter, some colonies died within a short time and the bees lay dead in the box (in Spain, hives usually remained empty). Whether these features are related to the new form of ''Nosema'' cannot be conclusively proven.


Transmission

Newly emerged bees are always free from infection. Spores must be swallowed by a bee for the infection to be initiated. The most common modes of transmission are fecal-oral and oral-oral, and it has been suggested that ''Nosema'' can be transmitted sexually in
honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
s. Spores germinate quickly after entering the insect, and the epithelial cells of the ventriculus are infected when the vegetative stage is introduced by way of the hollow polar filament. Once inside a cell, the vegetative stage increases in size and multiplies, effecting an apparent concurrent reduction of
RNA synthesis Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called ...
in the
host cell In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...
. In six to 10 days, the infected host epithelial cells become filled with new spores. Epithelial cells are normally shed into the ventriculus where they burst – releasing
digestive enzyme Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anima ...
s. When infected cells are shed similarly, they release 30–50 million infective spores when they burst.


Effects on the hive

''Nosema'' spores are spread to other colony members through fecal matter. The disease impairs the digestion of pollen, thereby shortening the life of the bee. A greater proportion of worker bees become infected than drones or queens, probably due to the comb-cleaning activities of young bees in which drones and queens do not participate. ''Nosema''-infected bees do not attend or feed the queen to the same extent as healthy bees, which helps the queen to escape infection. When the queen becomes infected, her ovaries degenerate and her egg-laying capacity is reduced due to atrophy of the
oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The femal ...
s. Queens that become infected by the parasite during the brood-rearing season are superseded by the bees. The seasonal trend of typical infections exhibits low levels during summer, a small peak in autumn, and a slow rise of infection during winter. It is more common during times of confinement - winter and spring. In the spring, the level of infection increases rapidly as brood-rearing starts and while flight possibilities are still limited. Colonies in northern climates are more seriously affected than colonies in the south because of the increased amount of time bees are confined in the hive. ''Nosema'', if left untreated, can cause queen supersedure, winter kills, reduced honey yields, and dwindling populations.


Diagnosis

Diagnosis is dependent on microscopic examination of the ventricular (midgut) content and/or
fecal matter Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
or on PCR analysis of infected tissue. No specific outward sign of disease may be present, although in dissections, the ventriculus often appears whitish and swollen in late stages of infection. The disease is easily detected in samples of whole bees macerated in water. The fluid is examined under a light microscope at 250–500 x magnification where the characteristic ''Nosema'' spores can be observed. Though the spores of ''N. apis'' and ''N. ceranae'' have slight morphological and ultrastructural differences, they cannot be reliably differentiated via light microscopy. PCR analysis or electron microscopy of spores are the only reliable ways to differentiate between the two types of ''Nosema'' infection, given genetic variation and variation in the number of sporular polar filament coils between the two species.


Treatment

Treatment with the antibiotic Fumidil B (prepared from '' Aspergillus fumigatus'', the causative agent of stonebrood), inhibits the spores reproducing in the ventriculus, but does not kill the spores. A disinfection of the honeycombs and utensils is recommended for an extensive disease outbreak. The spores are sensitive to chemicals such as acetic acid and
formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
, and physical radiation:
ultrasonic Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...
and gamma radiation. Heat treatment in 49 °C (120 °F) for 24 hours can be used to kill the spores on contaminated equipment.


See also

* Antibiotics * Diseases of the honeybee


References


Nosema ceranae – a new threat to Apis mellifera honey bees
University of Georgia , mottoeng = "To teach, to serve, and to inquire into the nature of things.""To serve" was later added to the motto without changing the seal; the Latin motto directly translates as "To teach and to inquire into the nature of things." , establ ...
Honeybee Program

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...
IFAS Extension, Malcolm t. Sanford

Swedish University of Agricultural Sciences The Swedish University of Agricultural Sciences, or Swedish Agricultural University (Swedish: ''Sveriges lantbruksuniversitet'') (SLU) is a university in Sweden. Although its head office is located in Ultuna, Uppsala, the university has several c ...
Ingemar Fries, 1993 *T.A. Gochauer, B. Furgala, H. Shimanuki: ''The Hive and the honeybee''. Chapter 21 ''Diseases and enemies of the honey bee'', Dadant 1975. *Higes, Mariano; u. a.: ''El Síndrome de Despoblamiento de las Colmenas en España'' (The bee dying syndrome in Spain). In: ''Vida Apícola'' 133 (September/October 2005), 15–21 (Montagud Editores,
Barcelona Barcelona ( , , ) is a city on the coast of northeastern Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second most populous municipality of Spain. With a population of 1.6 million within ci ...
, Spain). *Higes, Mariano; u. a.: ''Nosema ceranae, a new microsporidian parasite in honeybees in Europe''. In: ''Journal of Invertebrate Pathology'' 91 (2006) (
Elsevier Elsevier () is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its products include journals such as '' The Lancet'', ''Cell'', the ScienceDirect collection of electronic journals, '' Trends'', ...
). *Huang, Wei-Fone; u. a.: ''Complete rRNA Sequence of the Nosema ceranae from honeybee (Apis mellifera)''. National Taiwan University,
Taipeh Taipei (), officially Taipei City, is the capital and a special municipality of the Republic of China (Taiwan). Located in Northern Taiwan, Taipei City is an enclave of the municipality of New Taipei City that sits about southwest of the n ...
2005. *Huang, Wei-Fone; Jianga, Jing-Hao; Chenb, Yue-Wen and Wang, Chung-Hsiun
A Nosema ceranae isolate from the honeybee Apis mellifera
Apidologie 38 (2007) 30–37 *Klee, J., Besana, A. M., Genersch, E., Gisder, S., Nanetti, A., Tam, D. Q., Chinh, T. X., Puerta, F., Ruz, J. M., Kryger, P., Message, D., Hatjina, F., Korpela, S., Fries, I. & Paxton, R. J. (2007
Widespread dispersal of the microsporidium Nosema ceranae, an emergent pathogen of the western honey bee, Apis mellifera.
Journal of Invertebrate Pathology. *Webster, Thomas C.; u. a.: ''Nosema apis infection in worker and queen Apis mellifera'' / ''Nosema-apis-Infektion von Arbeiterinnen und Königinnen (Apis mellifera)''. In: ''Apidologie'' 35 (2004), 49–54 (EDP Sciences, Les Ulis, France). *Chioveanu, G., Ionescu, D., Mardare, A.
Control of Nosemosis – treatment with "Protofil"
Apiacta 39 (2004), S.31–38.


External links



at the University of Georgia, with a large section on Honey Bee Disorders]
Apiculture Factsheets
at the British Columbia Ministry of Agriculture and Lands
BeeBase
at the Department for Environment, Food and Rural Affairs, Defra Food and Environment Research Agency in the UK
Kohala.net
Diseases and Afflictions of Honey Bees
Beediseases
Honey bee diseases website by Dr. Guido Cordoni. {{DEFAULTSORT:Nosema Apis Western honey bee pests Microsporidia Articles containing video clips Beekeeping Fungi described in 1909