Thomas Jaenson

Uppsala University, Department of Organismal Biology, Subdepartment of Systematic biology, Faculty Member

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Professor in Medical Entomology at Uppsala University, Uppsala, Sweden.Field and laboratory studies on tsetse fly ecology and behaviour in Kenya 1975-1977, under the auspices of ICIPE Research Centre, Nairobi.PhD 1978, Uppsala University.Research scientist, sterile-male technique for control/eradication of tsetse flies

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USAMV Cluj Napoca

University of Messina

ErasmusMC Rotterdam

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Papers by Thomas Jaenson

Detection and prevalence of Anaplasma phagocytophilum and Rickettsia helvetica in Ixodes ricinus ticks in seven study areas in Sweden

Parasites & Vectors

Tick-borne Anaplasma phagocytophilum and Rickettsia spp. are considered to be emerging human path... more Tick-borne Anaplasma phagocytophilum and Rickettsia spp. are considered to be emerging human pathogens, but only limited data are available on their occurrence in Sweden. Two real-time PCR assays followed by nested PCR and sequence analysis were carried out to investigate the prevalence of A. phagocytophilum and spotted fever rickettsiae in ticks from seven areas in Sweden. In 139 pooled samples, representing a total of 1245 Ixodes ricinus ticks (204 larvae, 963 nymphs, 38 males, 40 females), the overall positive mean infection prevalence was 1.3-15.0% for A. phagocytophilum and 1.5-17.3% for R. helvetica. A. phagocytophilum was only detected in nymphs (1.7-19.4%), whereas R. helvetica was detected in all three tick stages. Support for vertical and transstadial transmission was only obtained for R. helvetica. Both agents showed similar infection rates across study areas, although infection rates were greater in coastal areas. The results show that both pathogens occurred in all seve...

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Relationship between Ixodes ricinus density and prevalence of infection with Borrelia-like spirochetes and density of infected ticks

Journal of medical entomology, 1996

During 1994-1995 we examined the density of questing Ixodes ricinus (L.) nymphs and their prevale... more During 1994-1995 we examined the density of questing Ixodes ricinus (L.) nymphs and their prevalence of infection with Borrelia-like spirochetes at 43 localities in south-central Sweden with median nymphal densities ranging from 0.1 to > 50/100 m2. The general pattern was that the infection prevalence in nymphs increased with nymphal density at < 10 nymphs per 100 m2, peaked (20-30%) at 10-20 nymphs per 100 m2, and decreased at higher nymphal densities. A low infection prevalence (7-10%) in nymphs at 4 of the 5 localities with the highest nymphal densities (> 35 nymphs per 100 m2) at the small island of Bedarön was most likely related to the presence of large numbers of fallow deer, Dama dama (L.), which are reservoir-incompetent for Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner. However, because the increase in nymphal density at Bedarön was greater than the decrease in infection prevalence, 5 of the 6 highest densities of infected nymphs occurred ...

Premature proposal of the pine weevil as a vector of a human pathogen

by Niklas Björklund and Thomas Jaenson

Journal of clinical microbiology, 2014

Dataset

[2011 peaks the TBE incidence. The deer tribe variation in size and the weather are key factors]

Läkartidningen

European reservoir hosts of Borrelia burgdorferi sensu lato

Zentralblatt für Bakteriologie : international journal of medical microbiology, 1998

Existing knowledge on reservoir hosts of Borrelia burgdorferi sensu lato was collated and reviewe... more Existing knowledge on reservoir hosts of Borrelia burgdorferi sensu lato was collated and reviewed and several species, particularly birds, were identified as reservoir competent. At the present time, 9 small mammals, 7 medium-sized mammals and 16 bird species, including passerines, sea birds and pheasants, appear to be capable of transmitting spirochaetes to ticks and thus of participating in the natural circulation of B. burgdorferi s.l. in Europe. The house mouse, Mus musculus is strongly suspected of reservoir competence and many other small rodent species, particularly in eastern Europe and Russia, have been implicated. Ungulates are not thought to play a major role as reservoir hosts, though co-feeding transmission may permit some tick infection. The criteria for establishment of reservoir status are outlined and a method for identification of host blood meals of previous instars of unfed ticks, developed in a participant laboratory, is briefly described.

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Infestation of mammals by Ixodes ricinus ticks (Acari: Ixodidae) in south-central Sweden

Experimental & applied acarology, 1997

Infestation by Ixodes ricinus ticks on rodents, hares and cervids was examined at Bogesund, 10 km... more Infestation by Ixodes ricinus ticks on rodents, hares and cervids was examined at Bogesund, 10 km north of Stockholm, in south-central Sweden during 1991-1994 and on varying hares (Lepus timidus) at Stora Karlsö and Gotska Sandön in the Baltic Sea during 1992-1993. At Bogesund, there were great differences between two consecutive years in the number of I. ricinus larvae infesting bank voles (Clethrionomys glareolus). The seasonal pattern of infestation by I. ricinus larvae and nymphs on bank voles was unimodal in 1991, with peaks in June-July and bimodal in 1992, with peaks in June and August. Male bank voles, compared to females and older voles, compared to young voles, harboured greater numbers of I. ricinus ticks. Apodemus mice, compared to bank voles, harboured greater numbers of I. ricinus ticks. Ixodes ricinus larvae engorged on Apodemus mice were heavier than larvae engorged on bank voles and resulted in larger nymphs. However, there was no difference in the proportions of vi...

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Transmission of mixed malaria species and strains by mosquitoes, as detected by PCR, in a study area in Guinea-Bissau

Parassitologia, 1997

Parasites present in blood samples of asymptomatic carriers and in the midgut of mosquitoes colle... more Parasites present in blood samples of asymptomatic carriers and in the midgut of mosquitoes collected within a few days from the same households, have been analysed by PCR. A high prevalence (32%) of infected mosquitoes was observed and, in half of these, two parasite species were found simultaneously. The distribution of parasite species in the mosquito correlated with that found in the infected persons. Genotype patterns of Plasmodium falciparum populations were however found to be different in the two sets of samples. These results and the potential of PCR are discussed with reference to investigations of the dynamics of malaria transmission.

Simplified methodology for PCR investigation of midguts from mosquitoes of the Anopheles gambiae complex, in which the vector and Plasmodium species can both be identified

Annals of tropical medicine and parasitology, 1997

Seasonal variations in density of questing Ixodes ricinus (Acari: Ixodidae) nymphs and prevalence of infection with B. burgdorferi s.l. in south central Sweden

Journal of medical entomology, 1996

Seasonal variations in the density of questing Ixodes ricinus (L.) nymphs and their prevalence of... more Seasonal variations in the density of questing Ixodes ricinus (L.) nymphs and their prevalence of infection with Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner were studied during 1991-1993 at a locality in southcentral Sweden. The seasonal pattern of the density of questing I. ricinus nymphs was variable; there was a bimodal pattern with peaks of similar magnitude in 1991, a bimodal pattern with a small spring peak and a greater autumn peak in 1992, and a unimodal pattern with a spring peak and lower values during summer and autumn in 1993. The seasonal pattern of prevalence of Borrelia infection in questing nymphs was similar during all 3 yr, with a peak infection prevalence in late spring or early summer, followed by lower infection prevalences in late summer and autumn. There was a significant correlation between the monthly density of Borrelia-infected nymphs and the monthly density of nymphs. This suggests that, within a certain range of nymphal densiti...

Transhemispheric exchange of Lyme disease spirochetes by seabirds

Journal of clinical microbiology, 1995

Lyme disease is a zoonosis transmitted by ticks and caused by the spirochete Borrelia burgdorferi... more Lyme disease is a zoonosis transmitted by ticks and caused by the spirochete Borrelia burgdorferi sensu lato. Epidemiological and ecological investigations to date have focused on the terrestrial forms of Lyme disease. Here we show a significant role for seabirds in a global transmission cycle by demonstrating the presence of Lyme disease Borrelia spirochetes in Ixodes uriae ticks from several seabird colonies in both the Southern and Northern Hemispheres. Borrelia DNA was isolated from I. uriae ticks and from cultured spirochetes. Sequence analysis of a conserved region of the flagellin (fla) gene revealed that the DNA obtained was from B. garinii regardless of the geographical origin of the sample. Identical fla gene fragments in ticks obtained from different hemispheres indicate a transhemispheric exchange of Lyme disease spirochetes. A marine ecological niche and a marine epidemiological route for Lyme disease borreliae are proposed.

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Maintenance by hares of European Borrelia burgdorferi in ecosystems without rodents

Journal of medical entomology, 1993

During May-October 1991 shrews (Sorex spp.), small rodents (Apodemus spp., Clethrionomys glareolu... more During May-October 1991 shrews (Sorex spp.), small rodents (Apodemus spp., Clethrionomys glareolus [Schreber]), and hares (Lepus spp.) were sampled near Stockholm, Sweden. Nymphal Ixodes ricinus (L.) derived from blood-engorged larvae collected from these mammals were investigated by phase-contrast microscopy and immunofluorescence assay (IFA) using the monoclonal antibody H6831 directed against the OspB protein of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner. Three rodent species, previously known as vertebrate reservoirs for B. burgdorferi in Switzerland, are competent reservoirs of Lyme borreliosis also in Sweden. The first data are presented showing Lyme disease reservoir competency of European insectivores (Sorex araneus L., S. minutus L.) and lagomorphs (Lepus europaeus Pallas, L. timidus L.). Lagomorphs are the only European vertebrates known to be both competent reservoirs for B. burgdorferi and a source of blood for all stages of I. ricinus. We propose ...

Seasonal variation in the capacity of the bank vole to infect larval ticks (Acari: Ixodidae) with the Lyme disease spirochete, Borrelia burgdorferi

Journal of medical entomology, 1993

Seasonal variation in the capacity of bank voles, Clethrionomys glareolus (Schreber), to infect l... more Seasonal variation in the capacity of bank voles, Clethrionomys glareolus (Schreber), to infect larval Ixodes ricinus (L.) ticks with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was examined from May through October 1991 at Bogesund, near Stockholm in south-central Sweden. Although larval infestations of bank voles were greatest in June and July, nearly 70% of all larval ticks infected with spirochetes by bank voles at this site became infected during August and September. Seasonality of infectivity was related to the degree of earlier nymphal infestation on voles as well as to the age composition of the vole population. These factors may influence the infectivity of other rodent reservoirs of B. burgdorferi, both in Europe and North America. Moreover, in determining the reservoir potential of tick hosts, a host population's spirochetal infectivity should be determined for the entire period of larval infestation rather than just during the period of peak la...

Geographical distribution, host associations, and vector roles of ticks (Acari: Ixodidae, Argasidae) in Sweden

Journal of medical entomology, 1994

This review covers the geographic distribution and host relationships of the tick species in Swed... more This review covers the geographic distribution and host relationships of the tick species in Sweden. Ixodes uriae White, I. caledonicus Nuttall, I. unicavatus Neumann, I. arboricola Schulze & Schlottke, and I. lividus Koch are ornithophagous species. I. trianguliceps Birula, I. canisuga Johnston, I. hexagonus Leach, and Argas vespertilionis (Latreille) are mammalophagous. I. ricinus (L.) and Haemaphysalis punctata Canestrini & Fanzago feed on both birds and mammals. All these tick species may be considered to be permanently present in Sweden. I. persulcatus Schulze, Hyalomma marginatum Koch, and the brown dog tick, Rhipicephalus sanguineus (Latreille), may be regarded as not indigenous to Sweden although they may be regularly introduced by spring-migrating birds or imported dogs, respectively. The first European record of the American dog tick, Dermacentor variabilis (Say), is reported. There are several records of Hyalomma aegyptium (L.) from imported tortoises in Sweden. Excluding...

Transmission of Borrelia burgdorferi s.l. from mammal reservoirs to the primary vector of Lyme borreliosis, Ixodes ricinus (Acari: Ixodidae), in Sweden

Journal of medical entomology, 1994

Factors regulating prevalence of Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & B... more Factors regulating prevalence of Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner in Ixodes ricinus (L.) were examined during 1991-1992 at Bogesund, near Stockholm in south-central Sweden. Nine species of small and medium-sized mammals (Sorex araneus L., S. minutus L., Neomys fodiens Pennant, Clethrionomys glareolus [Schreber], Microtus agrestis [L.], Apodemus sylvaticus [L.], A. flavicollis [Melchior], Lepus europaeus Pallas, L. timidus L.) were found to infect feeding tick larvae with B. burgdorferi s.l., whereas two species of large mammals (Capreolus capreolus L., Alces alces L.) failed to infect feeding tick larvae with this spirochete. The most important mammalian reservoirs at the study locality were S. araneus and rodents, accounting for 91% of all I. ricinus larvae infected. In view of the great number of potentially effective reservoirs for B. burgdorferi s.l. in Sweden, control of Lyme disease by reduction of abundance of reservoir hosts will be diff...

Attraction of Glossina longipalpis (Diptera: Glossinidae) in Guinea-Bissau to odor-baited biconical traps

Journal of medical entomology, 1991

The catches of tsetse flies, Stomoxys, and tabanids in biconial traps baited with different synth... more The catches of tsetse flies, Stomoxys, and tabanids in biconial traps baited with different synthetic odors were compared in the Jopá-Cobiana Forest, northwestern Guinea-Bissau. Thirty-six traps, the baits of which were randomly interchanged each of 10 sampling days, were baited either with (a) 1-octen-3-ol (octenol) + phenols [4-methylphenol + 3-propylphenol] + acetone + N'dama cow urine ("urine"), (b) octenol + phenols + acetone, (c) octenol + phenols, (d) acetone, (e) acetone + urine, or (f) urine. Six of the traps were not baited (controls). A total of 3,172 tsetse flies (96% Glossina longipalpis Widemann, 3% G. morsitans submorsitans Newstead, and 1% G. palpalis gambiensis Vanderplank), 286 Stomoxys, and 571 Tabanidae was captured. G. longipalpis was caught in statistically greater numbers in traps baited with octenol + phenols + acetone. Traps baited with octenol + phenols, with or without acetone, caught the greatest numbers of tabanids. N'dama urine did not...

Incompetence of roe deer as reservoirs of the Lyme borreliosis spirochete

Journal of medical entomology, 1992

To determine whether the roe deer, Capreolus capreolus L. may serve as a reservoir host for the L... more To determine whether the roe deer, Capreolus capreolus L. may serve as a reservoir host for the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, evidence of spirochetal infection was sought in nymphal Ixodes ricinus (L.) that had engorged as larvae on roe deer. Sixteen roe deer were shot in Lyme disease enzootic areas of south-central Sweden during August-November 1990 and August 1991. An average of 276 (range, 84-658) larvae of I. ricinus was collected from each of 12 deer shot in August. Of those ticks that had fed on deer and then developed to the nymphal stage, the gut contents of 238 were examined by phase-contrast microscopy. All these ticks were negative for spirochetes, whereas 4.2% contained Trypanosoma cf. cervi Kingston & Morton and 15.1% contained the nematode Dipetalonema rugosicauda Meszaros & Sugar. A total of 396 nymphal ticks was collected by blanket-dragging during May-June 1991 and examined for spirochetes; 9.1% of these ...

Lyme borreliosis awareness

Zentralblatt für Bakteriologie : international journal of medical microbiology, 1998

A Lyme borreliosis information leaflet has been produced to promote awareness amongst the general... more A Lyme borreliosis information leaflet has been produced to promote awareness amongst the general public. It was designed to provide a framework for similar material throughout Europe and complements a questionnaire produced to measure awareness of Lyme borreliosis. This questionnaire can be used to determine the impact of educational campaigns using material such as the leaflet. Feasibility studies showed that the questionnaire successfully highlighted predictable differences between sample groups and also that the leaflet performed well in increasing knowledge in low-awareness groups.

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Migratory birds, ticks, and Bartonella

Infection Ecology & Epidemiology, 2011

Bartonella spp. infections are considered to be vector-borne zoonoses; ticks are suspected vector... more Bartonella spp. infections are considered to be vector-borne zoonoses; ticks are suspected vectors of bartonellae. Migratory birds can disperse ticks infected with zoonotic pathogens such as Rickettsia and tickborne encephalitis virus and possibly also Bartonella. Thus, in the present study 386 tick specimens collected in spring 2009 from migratory birds on the Mediterranean islands Capri and Antikythera were screened for Bartonella spp. RNA. One or more ticks were found on 2.7% of the birds. Most ticks were Hyalomma rufipes nymphs and larvae with mean infestation rates of 1.7 nymphs and 0.6 larvae per infested bird. Bartonella spp. RNA was not detected in any of the tick specimens.

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Triatoma ryckmani (Hemiptera: Reduviidae) in the epiphyte Tillandsia xerographica (Bromeliaceae) in the semiarid region of Guatemala

Journal of medical entomology, 2004

For the first time, the reduviid bug Triatoma ryckmani Zeledón and Ponce (Hemiptera; Reduviidae) ... more For the first time, the reduviid bug Triatoma ryckmani Zeledón and Ponce (Hemiptera; Reduviidae) was recorded to inhabit the epiphyte Tillandsia xerographica Rohweder (Bromeliaceae) in the semiarid region of Guatemala. These bromeliads grow mainly in drought-resistant trees with rough bark such as Pereskia lychnidiflora (Cactaceae). In our study site, we investigated 30 T. xerographica, and 53 specimens of T. ryckmani were found. Most T. ryckmani (68.5%) were unfed. Ants (Formicidae) were the predominant (92.2%) insect taxon in T. xerographica. Other insects such as Blattidae (3.0%), Reduviidae (T. ryckmani: 2.5%), Blaberidae (2.2%), Gryllidae (0.1%), and Acrididae (0.1%) were recorded in the bromeliads. T. xerographica is illegally commercialized without previous inspection. This may cause accidental introduction of T. ryckmani to houses and to other countries.

Detection and prevalence of Anaplasma phagocytophilum and Rickettsia helvetica in Ixodes ricinus ticks in seven study areas in Sweden

Parasites & Vectors

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Relationship between Ixodes ricinus density and prevalence of infection with Borrelia-like spirochetes and density of infected ticks

Journal of medical entomology, 1996

Premature proposal of the pine weevil as a vector of a human pathogen

by Niklas Björklund and Thomas Jaenson

Journal of clinical microbiology, 2014

Dataset

[2011 peaks the TBE incidence. The deer tribe variation in size and the weather are key factors]

Läkartidningen

European reservoir hosts of Borrelia burgdorferi sensu lato

Zentralblatt für Bakteriologie : international journal of medical microbiology, 1998

Download

Infestation of mammals by Ixodes ricinus ticks (Acari: Ixodidae) in south-central Sweden

Experimental & applied acarology, 1997

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Transmission of mixed malaria species and strains by mosquitoes, as detected by PCR, in a study area in Guinea-Bissau

Parassitologia, 1997

Simplified methodology for PCR investigation of midguts from mosquitoes of the Anopheles gambiae complex, in which the vector and Plasmodium species can both be identified

Annals of tropical medicine and parasitology, 1997

Seasonal variations in density of questing Ixodes ricinus (Acari: Ixodidae) nymphs and prevalence of infection with B. burgdorferi s.l. in south central Sweden

Journal of medical entomology, 1996

Transhemispheric exchange of Lyme disease spirochetes by seabirds

Journal of clinical microbiology, 1995

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Maintenance by hares of European Borrelia burgdorferi in ecosystems without rodents

Journal of medical entomology, 1993

Seasonal variation in the capacity of the bank vole to infect larval ticks (Acari: Ixodidae) with the Lyme disease spirochete, Borrelia burgdorferi

Journal of medical entomology, 1993

Geographical distribution, host associations, and vector roles of ticks (Acari: Ixodidae, Argasidae) in Sweden

Journal of medical entomology, 1994

Transmission of Borrelia burgdorferi s.l. from mammal reservoirs to the primary vector of Lyme borreliosis, Ixodes ricinus (Acari: Ixodidae), in Sweden

Journal of medical entomology, 1994