Wolbachia is a maternally inherited α-proteobacteria that lives an obligate intracellular lifestyle in its eukaryotic hosts. Wolbachia pipientis was first identified in the 1920’s in the mosquito Culex pipiens; Wolbachia has since been detected in a broad range of hosts. Wolbachia induces a number of diverse reproductive manipulations in many of its hosts, implicating Wolbachia in control strategies for target species. However, changes in host bacterial interactions can evolve toward mutualism, and this requires investigation in target systems. / This first part of this work examines changes in the Drosophila simulans-Wolbachia Riverside system in California. This system, studied for a period of more than two decades, provides a rare example in nature of a symbiotic relationship shifting from parasitism to mutualism. In my study, no changes in overall estimates of infection frequency, maternal transmission or cytoplasmic incompatibility were found, however there appears to be heterogeneity in maternal transmission rates and the ability of males to induce cytoplasmic incompatibility (CI). The source of CI variation in one isofemale line was subsequently investigated through reciprocal backcrossing with an old Wolbachia-infected strain, Riv88, and the variation was attributed to the Wolbachia genome. Further investigations are required to determine the extent of CI variation in the wild. These findings significant implications for the many applied projects that intend to exploit Wolbachia for its ability to manipulate host reproductive systems. / The second part of this work investigates the extent to which evolution of a host-bacterial symbiosis can influence the effectiveness of control strategies using Wolbachia. A particular strain of Wolbachia, named popcorn (wMelPop), has been isolated for its ability to reduce host longevity. This bacterium has the capacity to alter the age structure of the target host populations. As many vector-borne diseases (eg: Dengue Fever, Malaria) require an incubation period within the vector prior to transmission to the final host, a reduction in the lifespan of vector populations has the potential to lower transmission levels. The long term stability of this bacterial strain has been investigated in its native host (Drosophila melanogaster), and a novel host (D. simulans). The longevity-shortening phenotype and several life-history traits that might influence the effectiveness of control strategies have been examined. Host genetic background and the indirect selection on the longevity phenotype (via early or late fecundity selection) were found to influence multiple life-history traits in these species. The source of this variation in D. melanogaster is attributed primarily to the host, but can also be influenced by Wolbachia. Strong host background effects were noted in D. simulans, which highlights the importance of testing multiple backgrounds for suitability of use in applied projects. / This work has allowed for greater understanding of the potential for evolution within host-symbiont systems, and can be used to provide a framework for undertaking projects that will use Wolbachia as biological control agents. Future projects should consider the potential for evolution in detail under laboratory conditions before control strategies are implemented in the wild.

Wolbachia is a maternally inherited α-proteobacteria that lives an obligate intracellular lifestyle in its eukaryotic hosts. Wolbachia pipientis was first identified in the 1920’s in the mosquito Culex pipiens; Wolbachia has since been detected in a broad range of hosts. Wolbachia induces a number of diverse reproductive manipulations in many of its hosts, implicating Wolbachia in control strategies for target species. However, changes in host bacterial interactions can evolve toward mutualism, and this requires investigation in target systems. / This first part of this work examines changes in the Drosophila simulans-Wolbachia Riverside system in California. This system, studied for a period of more than two decades, provides a rare example in nature of a symbiotic relationship shifting from parasitism to mutualism. In my study, no changes in overall estimates of infection frequency, maternal transmission or cytoplasmic incompatibility were found, however there appears to be heterogeneity in maternal transmission rates and the ability of males to induce cytoplasmic incompatibility (CI). The source of CI variation in one isofemale line was subsequently investigated through reciprocal backcrossing with an old Wolbachia-infected strain, Riv88, and the variation was attributed to the Wolbachia genome. Further investigations are required to determine the extent of CI variation in the wild. These findings significant implications for the many applied projects that intend to exploit Wolbachia for its ability to manipulate host reproductive systems. / The second part of this work investigates the extent to which evolution of a host-bacterial symbiosis can influence the effectiveness of control strategies using Wolbachia. A particular strain of Wolbachia, named popcorn (wMelPop), has been isolated for its ability to reduce host longevity. This bacterium has the capacity to alter the age structure of the target host populations. As many vector-borne diseases (eg: Dengue Fever, Malaria) require an incubation period within the vector prior to transmission to the final host, a reduction in the lifespan of vector populations has the potential to lower transmission levels. The long term stability of this bacterial strain has been investigated in its native host (Drosophila melanogaster), and a novel host (D. simulans). The longevity-shortening phenotype and several life-history traits that might influence the effectiveness of control strategies have been examined. Host genetic background and the indirect selection on the longevity phenotype (via early or late fecundity selection) were found to influence multiple life-history traits in these species. The source of this variation in D. melanogaster is attributed primarily to the host, but can also be influenced by Wolbachia. Strong host background effects were noted in D. simulans, which highlights the importance of testing multiple backgrounds for suitability of use in applied projects. / This work has allowed for greater understanding of the potential for evolution within host-symbiont systems, and can be used to provide a framework for undertaking projects that will use Wolbachia as biological control agents. Future projects should consider the potential for evolution in detail under laboratory conditions before control strategies are implemented in the wild.

In recent decades, mental illness has increased in Sweden, and in parallel to this there has been an increase in unemployment. This implies that it is harder for people who have been away from employment for long periods due to ill health to return to work. The purpose of this study was to examine the work situation of people with mental illness who had undergone prevocational training, and to identify psychosocial factors relevant to their current work ability. The aim was also to describe how those who had undergone prevocational training perceived that it had affected their work ability. The study involved 19 participants who were interviewed and assessed with the Worker Role Interview, and an open question was asked about how they perceived that the prevocational training had affected their current work ability. The interview revealed that three of the participants were on sick leave, one was seeking a job, and 15 were working or studying. The results showed that the participants generally had support to acquire, return to, or continue employment concerning the psychosocial factors identified with the WRI. The WRI items showing the strongest support concerned the participants’ understanding of their abilities and limitations, their belief in their ability to work, and their understanding of what the working role involved. All participants perceived that the prevocational training had had a significant impact on their ability to return to work.

Introduktion: Sjukfrånvaron i Sverige är hög och kunskap om vad som påverkar återgång i arbete efter sjukskrivning behöver utvecklas. I processen kring återgång i arbete är bedömning av arbetsförmåga en viktig del. Bristen på valida, reliabla och teoretiskt förankrade bedömningsinstrument inom området är dock ett bekymmer eftersom tillförlitliga bedömningar av arbetsförmåga är en förutsättning för utformning och genomförande av interventioner för att stödja återgång i arbete. Denna typ av interventioner kräver multidisciplinär kompetens där arbetsterapeuter utgör en viktig funktion. Vid bedömning av arbetsförmåga bör personens subjektiva uppfattning om sin situation beaktas, då den har betydelse för utfallet av återgång i arbete. Worker Role Interview (WRI) och Work Environment Impact Scale (WEIS) är två arbetsrelaterade intervjuinstrument, som har utvecklats i syfte att bedöma subjektiva psykosociala och miljömässiga faktorers påverkan på arbetsförmåga. Den teoretiska grunden till WRI och WEIS är Model of Human Occupation, som är en modell med fokus på aktivitetsutförande i relation till psykosociala faktorer. Inledande prövningar av WRI och WEIS reliabilitet och validitet har genomförts. Bedömningsinstrumenten har bearbetats och översatts till svenska och används främst av arbetsterapeuter, som arbetar med personer med arbetsrelaterad problematik. Syfte: Det övergripande syftet med avhandlingen är att undersöka användbarheten av bedömningsinstrumenten Worker Role Interview och Work Environment Impact Scale för identifiering av psykosociala och miljömässiga rehabiliteringsbehov av betydelse för återgång i arbete. Metod: Avhandlingen består av fem empiriska studier. I samtliga studier har erhållen information bearbetats kvantitativt. I studie IV har även kvalitativ bearbetning genomförts. Studie I, II och IV är tvärsnittsstudier och studie II och V är två års longitudinella studier. I studie I samlades information in via enkät. I studie II, III och V bestod den huvudsakliga informationen av skattningar utifrån WRI variabler och i studie IV var bedömningar utifrån WEIS i form av skattningar och nedskrivna kommentarer till skattningarna den huvudsakliga informationen. Resultat: I studie I undersöktes vilka teoretiska utgångspunkter och professionsspecifika modeller arbetsterapeuter i Sverige ansåg påverka den psykiatriska vården och den psykiatriska arbetsterapin. Det psykosociala perspektivet var den teoretiska utgångspunkt som hade störst påverkan både på psykiatrisk vård och på psykiatrisk arbetsterapi. Den arbetsterapeutiska modell som flest identifierade var Model of Human Occupation. Detta resultat indikerar att Model of Human Occupation verkar vara användbar inom arbetsterapi och motiverade vidare användning av modellen i denna avhandling. Det som dock också framkom i studie I var att arbetsterapeuter inom psykiatrisk vård använde professionsspecifika modeller i en relativt liten utsträckning. Ett sätt att öka tillämpningen av teori i praktik är att använda teoretiskt grundade bedömningsinstrument. I studie II, III, IV och V har endera av de Model of Human Occupation- baserade bedömningsinstrumenten WRI och WEIS använts och värderats. I studie II och V prövades WRI:s förmåga att predicera återgång i arbete efter långvarig sjukskrivning. Det område i WRI som uppvisade bäst prediktivitet var området ”Självuppfattning” vars variabler beaktar personens motivation för återgång i arbete i form av personens upplevelse av kompetens och effektivitet för att utföra arbetsuppgifter och hantera utmaningar i arbetet. De två WRI variabler som bäst kunde predicera vilka som skulle återgå respektive inte återgå i arbete vid uppföljning efter två år var: ”Tro på sin arbetsförmåga”, och ”Dagliga vanor och rutiner”. Resultaten tyder på att kunskap om hur tro på den egna förmågan stärks och kunskap om dagliga vanor och rutiners påverkan på utförande av arbete är central vid genomförande av interventioner i syfte att stödja personer att återgå till arbete efter sjukskrivning. I studie III prövades WRI:s konstrukturella validitet i en internationell studie. Samtliga variabler i WRI, förutom de som tillhör miljöområdet, uppvisade en god konstrukturell validitet dvs mätte psykosociala faktorers påverkan på arbetsförmågan. WRI:s skattningsskala verkar stabil och valid mellan olika länder och för personer med olika diagnoser. I analysen framkom att WRI kunde särskilja mellan personers psykosociala arbetsförmåga på tre olika nivåer. I studie IV undersöktes hur personer med erfarenhet av långtidssjukskrivning uppfattar att faktorer i arbetsmiljön stödjer respektive hindrar personens utförande av arbete och välbefinnande genom bedömningar utifrån WEIS. De faktorer som uppfattades som mest stödjande var olika former av sociala interaktioner på arbetet samt uppfattningen om arbetets värde och mening. De faktorer som uppfattades som mest hindrande var olika krav i relation till arbetsgenomförandet samt den belöning som erhålls för arbetet. Konklusion: Sammanfattningsvis så kan WRI användas för bedömning av psykosociala faktorers påverkan på arbetsförmågan. I WRI ingår variabler som kan predicera återgång till arbete upp till två år efter genomförd bedömning. WEIS verkar användbart för att identifiera arbetsmiljöfaktorer som stödjer respektive hindrar personers välbefinnande och utförande av arbete. Att komplettera olika datainsamlingsmetoder är en förutsättning för att uppnå en så god bedömning av arbetsförmåga som möjligt. Den information som WRI- och WEISintervjuer genererar är värdefull, då den kan utgöra en viktig grund för planering av individspecifika rehabiliteringsinsatser. Bedömningsinstrumenten WRI och WEIS med sin teoretiska förankring i Model of Human Occupation kan anses vara användbara för att identifiera psykosociala och miljömässiga rehabiliteringsbehov i syfte att stödja personer i processen åter till arbete efter sjukskrivning. / Introduction: In Swedish society the sick-leave rate is high and a better understanding is required of the factors that facilitate return to work. In the return to work process, assessments of peoples’ work ability play an important role. However, the lack of usable, valid, reliable, and theoretically sound assessment instruments for assessing work ability is a concern. Credible and theoretically sound assessment methods for assessing clients’ work ability strengthen the possibilities for making valid interpretations and obtaining important information for composing further intervention strategies which can guide suitable interventions in the process of returning to work. Such interventions need multi-professional expertise. In this area occupational therapists can offer valuable contribution. In the overall assessment of work ability the unique individual’s subjective perception of the situation needs to be considered since this has been found greatly relevant for return to work. The Worker Role Interview (WRI) and the Work Environment Impact Scale (WEIS) are two work-related interview assessment instruments that have been developed to assess subjective psychosocial and environmental factors of work ability. The WRI and the WEIS have been primarily tested for reliability and validity and are theoretically founded in the Model of Human Occupation (MOHO), which is an occupation-focused model addressing psychosocial factors. They have been adapted and translated to Swedish and are used among Swedish occupational therapists working with clients experiencing work-related problems. Aim: The overall aim of this thesis was to evaluate the usefulness of the assessment instruments the Worker Role Interview and the Work Environment Impact Scale for identifying psychosocial and environmental rehabilitation needs essential for returning to work. Methods: Five empirical studies were performed, all of which were analysed quantitatively, with the exception of study IV in which both qualitative and quantitative analysing methods were used. Studies I, III and IV were cross-sectional while studies II and V were two-year longitudinal studies. In study I, data were collected by a questionnaire, in studies II, III and V the primary data constituted of ratings on the WRI items. In study IV the primary data were ratings of the WEIS items and the written notes beside the rating on each item. Results: In study I, theoretical approaches and professional models that influenced psychiatric care and psychiatric occupational therapy practice among occupational therapists in Sweden was investigated. The most common approach in psychiatric care was the psychosocial approach, and the practice model which was most often used was the Model of Human Occupation. The results indicated that the psychosocial approach and the Model of Human Occupation seemed applicable in occupational therapy, motivating further use of that model. However, it was also found that occupational therapists in psychiatric care used professional practice models to a rather low extent. One way to enhance the application of theory into practice is the use of theory- based assessment instruments. Consequently, the Model of Human Occupation- based assessment instruments, the WRI and the WEIS, have been evaluated and used in the other studies in the present thesis The value of the WRI for predicting return to work after long term sick-leave was investigated in studies II and V. The content area in the WRI with best overall predictive validity for return to work was ‘Personal causation’. Its items focus on the individual’s motivation for return to work in relation to the individual’s feeling of competence and effectiveness in doing work tasks and facing challenges at work. The two WRI items which best predicted whether the participants would be in the working or the non-working groups at the two-year follow up were ‘Expectations of job success’, which concerns beliefs in personal abilities in relation to returning to work, and the item ‘Daily routines’ which concerns the individual’s routines and organisation of time outside work. These results suggest that knowledge about how to strengthen the person’s belief in his or her abilities, how routines impact occupational performance, and how to support the individual in structuring his or her daily doings are needed in interventions aiming at supporting the individual to return to work. In study III the construct validity of the WRI was investigated in an international study. All the WRI items except those related to the environment area seemed to capture the intended construct of the WRI, namely psychosocial ability for return to work. The construct of the WRI seems to be stable and valid across different countries and populations, and the WRI showed an ability to separate clients into three distinct levels of psychosocial ability for return to work. In study IV the impact of the work environment was investigated by using the WEIS among people with experiences of sick-leave. Social interactions at work and the meaning of the work had the most supportive impact and different work demands and the rewards received for the work were perceived as most interfering with work performance, well-being, and satisfaction. Conclusion: The WRI seems to be suitable for estimating psychosocial work ability. In addition it contains items which can predict return to work up to two years after the assessment is conducted. The use of the WEIS revealed supportive and interfering factors for work performance, well-being, and satisfaction among people with experiences of long term sick-leave. The interview format of the WRI and the WEIS seems valuable since it provides comprehensive information which can contribute to the planning of rehabilitation interventions for the unique client. Thus, the WRI and the WEIS, which are theoretically founded in the Model of Human Ocupation are juged to be useful for identifying psychosocial and environmental rehabilitation needs in order to support the individual in returning to work after sick-leave.