Respiratory Syncytial Virus, a threat for nursing homes residents?
Delphine Héquet (Lausanne | CH)
Nursing home residents live confined, in close contact with one another and staff, increasing opportunities for viral spread. During winter season, Respiratory Syncytial Virus (RSV) might affect the residents as much as influenza virus. However, data estimating RSV morbidity and mortality in nursing homes remain scarce.
In influenza seasons 2016-2017 and 2017-2018, a study on the burden of influenza was led in nursing homes of canton de Vaud. Nasal swabs were collected in residents symptomatic with an influenza-like illness. The samples were analyzed with a coupled PCR diagnosing influenza A/B as well as RSV. As a result, the diagnosis of RSV was underlined, even though it was not the purpose of the study.Demographic characteristics of resident were recorded (clinical data, hospitalization, mortality).
509 residents with influenza-like illness (ILI) symptoms were included. 38 RSV infected residents (7.5%) were diagnosed in 15 different nursing homes. 10 of these nursing homes experienced an epidemic situation with ≥2 residents diagnosed and 2 of them with 5 and 6 simultaneous cases respectively. Median age was 87 years (SD 7). Median temperature at diagnosis was 37.9°C (SD 1.1). The three most represented symptoms were cough (89.5%), malaise (73.7%) and fever (71.1%). 12 residents (31.2%) required oxygen therapy and 26 residents (68.4%) were treated with an antibiotic. 3 residents were hospitalized within 30 days after diagnosis (7.9%). 8 residents died within the first 30 days (21%) and a total of 14 residents died within 90 days (37%).
This study revealed that RSV infections in the institutionalized elderly is an underestimated threat. Residents with a RSV infection encounter a risk for hospitalization and mortality. Although the study was conducted on a relatively small number of residents, it reveals the need to take into account this pathogen in case of influenza-like illness outbreak in nursing home. Moreover, RSV outbreaks can occur in nursing homes. In case of influenza-like illness epidemic in a nursing home, if samples are negative for influenza, RSV should be looked for.
The management of invasive fungal disease prior hematopoietic stem-cell transplant and its effects on post-allogeneic fungal infections
Sabine Kuster (Basel | CH)
Objectives: Patients with prior invasive fungal disease (IFD) increasingly proceed to allogeneic hematopoietic cell transplantation (allo-HCT). Nevertheless, the optimal management of pre-existing IFD remains unclear. We investigated the management of patients with pre-existing IFD, the incidence of IFD and outcomes post-allogeneic HCT within the Swiss Transplant Cohort Study (STCS). Methods: The STCS is a prospective, clinic-based, observational study of HCT recipients since 2009. Data were collected on the diagnosis and treatment of IFD prior to allo-HCT by retrospective chart review from 01.2009 to 11.2013. Patients with pre-allo-HCT IFD were compared to non-IFD patients. Results: We included 456 allo-HCT recipients with 23 (5.0%) IFD prior to HCT: 8/23 (34.8%) invasive yeast infections (IYI) and 15/23 (65.2%) probable/proven invasive mold disease (IMD), consisting of 13 invasive aspergillosis and 2 non-Aspergillus IMD. Median time between IFD diagnosis and allo-HCT was 102 days [IQR 67;171] for all patients, 77 days [IQR 45;131] in IMD and 126 days [IQR 82;171] in IYI respectively. The vast majority (21/23, 91.3%) of patients with pre-allo-HCT IFD were transplanted during the first year after IFD-diagnosis: 7/8 (87.5%) and 14/15 (93.3%) of IYI and IMD patients, respectively. More than half (14/23; 60.9%) patients with pre-allo-HCT IFD received treatment with a single antifungal agent. Sequential treatment changes were documented in 7/23 (30.4%) patients. Initial antifungal treatment consisted of voriconazole (9/23, 39.1%), followed by echinocandins (7/23, 30.4%) and liposomal amphotericin-B (6/23, 26.1%). Treatment changes during conditioning were performed in 47.8% (11/23). Post-HCT, 87% (20/23) of IFD patients received mold-active antifungal treatment for median 7 months [range 1-27]. Additional surgical resection was performed in 9/23 (39.1%) patients. One-year probability of post-HCT IFD was 4.4% (1/23) and 8.3% (36/433) for IFD patients and non-IFD patients, respectively (P-value: ns). Overall one-year survival was 52.2 % (IFD patients) and 58.2% (non-IFD patients; P-value 0.021). Conclusion: Pre-allo-HCT IFD was not associated with higher post-allogeneic HCT IFD incidence or mortality. Careful management, including long-term appropriate antifungal treatment and pre-HCT surgical intervention with secondary post-HCT prophylaxis may contribute to beneficial outcomes. Larger studies are needed to optimally guide the management of these patients.
Malaria Standby Emergency Treatment (SBET) for Travelers Visiting Malaria Endemic Areas: a Systematic Review and Meta-Analysis
Rainer Tan (Lausanne | CH)
Malaria prevention methods for travelers to low or moderate malaria risk areas varies and remains controversial. Standby Emergency Treatment (SBET) for malaria is one possible strategy increasingly recommended since 1988 with little evidence on its effectiveness or how it is truly being used.
A systematic review and meta-analysis were performed based on a structured search in Embase, Medline, PubMed, Cochrane, and Web of Science on September 7, 2018. The primary outcome was the overall prevalence of SBET use in travelers, and secondary outcomes were the proportion carrying SBET, the response to fever (use of SBET, health facility attendance, use of malaria rapid diagnostic test [mRDT]), adverse events to SBET, and the proportion using SBET incorrectly (incorrect dosage/duration). The pooled SBET use prevalence was analyzed using a random-effects model. A descriptive summary was done to present secondary outcomes. The study protocol was registered with PROSPERO CRD42018103703.
11 studies were eligible for inclusion among the 1027 titles identified by our search. The studies included 7/11 prospective cohort studies that recruited pre-travel clinic attendees in Europe, and 4/11 cross-sectional studies, of which 3 recruited travelers at airports before their return home from South-East-Asia and Africa, and 1 from an employee registry including long-term travelers. The overall pooled prevalence of SBET use among the 26’403 travelers was 2.5% (95%CI 1.1%-4.3%; range 0.4%-10.8%). There was significant variation in the proportion of travelers carrying SBET medication (40%-100%), the proportion of travelers with appropriate response to fever (23%-100%), adverse events (0%-33%) and incorrect dosage/duration of SBET (0%-100%).
Adherence to the proposed recommendations for SBET use, notably the response to fever, was poor. If the use of SBET is to be pursued, modifications to the current SBET strategy should be considered, such as better selection of travelers at higher risk for malaria, and the potential addition of mRDTs.
Impact of Pseudomonas aeruginosa intracellular reservoir and antibiotic therapy on Pseudomonas lung infection
Eleonora Ciarlo (Epalinges, Lausanne | CH)
P. aeruginosa is considered an extracellular pathogen but it is also internalized by epithelial cells. Infection treatment relies, among others, on aminoglycosides and fluoroquinolones. Fluoroquinolones are highly diffusible molecules. Aminoglycosides display poor cell penetration. The consequences of bacteria internalization on cellular function and on response to antibiotics have not been studied. The type three secretion system (T3SS) is a virulence factor of P. aeruginosa, whose absence is associated with intracellular localization. CHA is cystic fibrosis clinical isolate of Pseudomonas. CHAΔpopBD is an isogenic mutant of CHA in which T3SS synthesis has been inactivated. We aim to characterize the impact of P. aeruginosa intracellular location on the behavior of lung epithelial cells and how antibiotic diffusion affects the response to intracellular and extracellular P. aeruginosa during infection.
A549 lung epithelial cells were incubated with CHA or CHAΔpopBD. Cells were either washed and lysed for intracellular bacteria enumeration, or treated with tobramycin or ciprofloxacin for ROS quantification using CM-H2DCFDA ROS sensitive dye. Cell death was obtained through MTT assay. Mice challenged with either CHA (3*106 CFU, i.n.) or CHAΔpopBD (8*107 CFU, i.n.) received 40 mg/kg of ciprofloxacin i.p.. Lung permeability was assessed 24 h post infection. The control group was not infected nor treated with antibiotics.
A459 internalize more CHAΔpopBD than CHA. Cell death was significantly higher when A549 were incubated with CHA. Antibiotic induced-ROS production by A549 is the highest when cells are treated with ciprofloxacin (fluoroquinolone with high cellular diffusion capacity) in the presence of intracellular bacteria. In a mouse model of lung infection where the inocula of CHA and CHAΔpopBD were titrated to produce similar lung injury, the subsequent treatment with ciprofloxacin worsened lung injury in both CHA and CHAΔpopBD infected mice compared to the non-treated infected mice. The antibiotic-induced increase in lung injury was more important in mice infected with CHAΔpopBD compared to mice infected with the wild type strain CHA.
The internalization of P. aeruginosa affects cell viability and both cell ROS production and mice response to antibiotic treatment during infection. Further work is ongoing to better understand how intracellular P. aeruginosa impact on lung infection and antibiotic treatment.
The TransFLUas influenza transmission study in acute healthcare – attack rates, symptoms and transmission clusters
Stefan P. Kuster (Zurich | CH)
Nosocomial acquisition of influenza from asymptomatic individuals may occur and is a major concern for infection control in hospitals. However, no prospective studies within acute care settings have studied transmission of influenza from asymptomatic individuals. In this study, we aimed to dissect transmission dynamics of influenza virus trajectories in a tertiary care hospital.
Materials and methods
This prospective study followed patients in medical wards and acute care healthcare workers (HCW) working on the same wards over two consecutive influenza seasons. Inpatients and acute care HCW provided mid-turbinate nasal swabs for multiplex real-time PCR and whole-genome sequencing. Illness diaries were recorded on a daily basis, and contacts between study participants were tracked.
We recruited 152 HCWs and 543 inpatients in the 2015/16 and 2016/17 influenza seasons. 16 (10.5%) of HCW and 19 (3.5%) of inpatients were diagnosed with an influenza infection. A total number of 1241 swabs were collected in these 35 subjects. Of these, 109 swabs tested positive. The number of positive swabs per individual ranged from 1 to 13. The majority of subjects (83.1% of HCW and 91.9% of patients) had influenza symptoms when their tests were positive, and this always included respiratory symptoms. However, 12/71 (16.9%) influenza-positive swabs among HCW and 3/37 (8.1%) influenza-positive swabs among patients were collected on days without symptoms. Among the symptomatic individuals, 2/14 (14.3%) of HCW and 0/17 inpatients had a positive influenza test before symptoms developed. 2/16 (12.5%) HCW and 2/19 inpatients (10.5%) remained asymptomatic. Preliminary analyses based on local and temporal proximity of HCW and inpatients revealed at least seven clusters of potential transmission events among HCW, among inpatients or between HCW and inpatients, and one cluster revealed a possible transmission from an asymptomatic HCW to an inpatient. Evidence, based on local and temporal proximity, for one possible transmission from an asymptomatic healthcare worker to an inpatient was not supported by phylogenetic analysis.
Influenza infection in acute care is common and a significant proportion of individuals shed influenza virus without harboring any symptoms, thereby potentially exposing their vicinity. Asymptomatic transmission seemed likely in one cluster, but was not supported by phylogenetic analyses.
Burden of respiratory virus infections in solid-organ transplant recipients: a nationwide multi-season cohort study
Matteo Mombelli (Lausanne | CH)
Purpose: Respiratory virus infections (RVI) are common in solid-organ transplant recipients (SOTr) and are caused by a wide range of viruses. However, beside influenza, little is known about the burden of RVI in SOTr. We aimed to study the burden of RVI in the Swiss Transplant Cohort Study (STCS): a large, nationwide cohort of SOTr including > 95 % of transplant performed in Switzerland.
Methods: For this study, patients participating to the STCS and transplanted between May 2008 and December 2015 were included. Infectious episodes were prospectively collected at each study center. Testing for RVI was performed as part of routine practice at each center. Additional clinical information not included in the STCS database was collected through chart review. Logistic regression was used to identify risk factors for severe RVI.
Results: Among 3308 patients [1834 (55 %) kidney, 687 (21 %) liver, 250 (8 %) heart, and 337 (10 %) lung transplant] with a median follow-up of 3.7 years (IQR 1.9 - 5.8), we identified 750 episodes of microbiologically documented RVI (26 % Influenza, 11 % Respiratory Syncytial virus, 7 % Parainfluenza virus, 4 % Human metapneumovirus, 35 % Rhinovirus, 10 % Coronavirus, 1 % Adenovirus, 0.7 % Bocavirus and 5 % mixed infections) in 442 patients (13 %). Estimated incidence was 61 cases per 1000 person-year. RVI was hospital acquired in 57 (8 %) of cases. RVI was asymptomatic in 62 / 592 (10 %), whereas lower respiratory tract infection was diagnosed in 266 / 592 (45 %) of RVI episodes. Among 343 RVI episodes, for which imaging was performed, pneumonia was diagnosed in 147 (43 %). Microbiologically-confirmed bacterial and fungal coinfection occurred in 8% and 4% of RVI. Hospital and Intensive Care Unit (ICU) admission-rates were 35% and 4%. In univariate analysis, Influenza (OR 2.2; P = 0.035), nosocomial infection (OR 6.9; P < 0.001), and microbiologically confirmed bacterial (OR 10.2; P < 0.001) and fungal coinfections (OR 4.8; P = 0.006) were associated with ICU admission.
Conclusions: In this nationwide, multiseason cohort, RVI in SOTr were associated with important morbidity. In particular, Influenza, nosocomial infection, and microbiologically confirmed coinfection, were associated with severe disease.
First detection of TR34/L98H Aspergillus fumigatus mutants in Switzerland
Silvio Ragozzino (Basel | CH)
Background: Azole resistance in Aspergillus fumigatus has emerged as a global health problem and has been associated with high mortality rates in patients with invasive aspergillosis. The aim of this study is to assess the distribution and antifungal susceptibility profile of clinical respiratory Aspergillus spp. isolates in Switzerland. Here we present first preliminary results.
Materials/methods: This prospective multicenter study was conducted at all hospitals participating in the Fungal Infection Network of Switzerland (FUNGINOS). A one-year period starting from January 2018 was covered. All patients with detection of Aspergillus spp. in a respiratory sample were included. The main demographic, clinical and microbiological data were collected according to a specific case report form. All isolates were sent to a central laboratory for antifungal phenotypic susceptibility testing by Sensititre YeastOne panel. Aspergillus isolates with high minimum inhibitory concentration (MIC) for one of the tested triazoles were analysed by complete sequencing of the cyp51A gene and promoter region for detection of mutations.
Results: In the first 8 months, 136 respiratory samples with Aspergillus spp. were included. Samples were obtained from sputum (n=80, 59%), bronchoalveolar lavage or tracheobronchial aspirate (44, 32%), lung biopsy (7, 5%) and others (5, 4%). The isolates consisted of A. fumigatus (n=104, 76%), A. niger (15, 11%), A. flavus (7, 5%) and others (10, 7%). Two A. fumigatus strains were resistant to azoles and were found to carry the typical environmental TR34/L98H mutation. The first isolate (Case 1) was obtained from a lung biopsy of a 62-year-old patient with proven invasive aspergillosis after allogeneic stem cell transplantation who had grade III graft-versus-host disease and had received long-term mold-active treatment. The other isolate (Case 2) was obtained from the sputum of a 73-year-old male patient with chronic obstructive pulmonary disease and was interpreted as colonisation.
Conclusions: The prevalence of azole resistance among respiratory Aspergillus spp. isolates in Switzerland is low (< 2%). We detected the first two cases of TR34/L98H A. fumigatus mutants in clinical isolates in our country.
How to develop and implement a computerized decision support system integrated with electronic prescribing for antimicrobial stewardship? Experience from two Swiss hospital systems.
Gaud Catho (Genève | CH)
Many antimicrobial stewardship (AMS) interventions require intensive human resources and are difficult to sustain in the long-term. Computerized decision support systems (CDSS) provide new opportunities for automating AMS interventions and integrating them in routine healthcare. CDSS are recommended as part of AMS programs by international guidelines (1), yet developing and implementing such systems faces several challenges that we wish to describe here.
We developed and implemented two CDSS integrated into the in-house electronic health records in three public hospitals in Switzerland (Geneva, Lugano and Bellinzona) in the context of the COMPASS study (2). The CDSS encourages physicians to follow local guidelines for antimicrobial therapy and duration of treatment and to regularly reevaluate treatment.
Despite a relatively simple algorithm without incorporation of much patient-specific data, the development of the system and its integration into the computerized physician order entry was complex and took between 9 (Ticino) and 12 months (Geneva). The trade-off between entering in the system structured data and providing a safe and user-friendly prescribing process through the user interfaces was challenging. The use of standardized terminologies to avoid free-text is essential for analysis purposes and long-term sustainability. The CDSSs have now been used in 12 wards for 8 (Ticino) and 5 months (Geneva) respectively. Feed-back based on the use of the system is delivered to end-users approximately every three months. One major challenge encountered is to get physicians to actively use the CDSS in case of transfer of patients who are already receiving antimicrobials (whereas the use of the system is automatic in case of prescriptions initiated in the unit). Users satisfaction survey showed a global satisfaction score of 3.3 for Ticino (18 answers) and 2.7 for Geneva (26 answers) on a 5-points Likert-scale. The main complaint by end-users is the extra-time required compared to the standard prescribing process.
When designing and developing a CDSS, close collaboration between an IT team with development expertise and clinicians is essential. End-users views and experience should be taken into account for future improvement. Future developments will be part of a more global clinical information system platform designed to support new CDSS COMPASS-like initiatives and adaptation of COMPASS for other areas (such as pediatrics).
Mycoplasma pneumoniae-induced mucocutaneous disease: a prospective longitudinal cohort study
Patrick M. Meyer Sauteur (Zürich | CH)
Objectives: To report the occurrence and clinical presentation of Mycoplasma pneumoniae-induced mucocutaneous disease in a prospective longitudinal cohort study of children with community-acquired pneumonia (CAP).
Methods: We investigated M. pneumoniae-induced mucocutaneous disease among 152 children enrolled during a prospective longitudinal CAP study from May 1, 2016, to April 30, 2017 at the University Children’s Hospital Zurich. Infection with M. pneumoniae was diagnosed by polymerase chain reaction (PCR) in pharyngeal samples and confirmed with the measurement of peripheral blood immunoglobulin (Ig) M antibody-secreting cells (ASCs) by enzyme-linked immunospot (ELISpot) assay.
Results: Mucocutaneous eruptions developed in 10 (23%) cases of CAP positive for M. pneumoniae by PCR (n = 44), all of whom tested positive for specific IgM ASCs. M. pneumoniae PCR-negative CAP cases had skin manifestations in 3% (p < 0.001). The spectrum of M. pneumoniae-induced mucocutaneous disease included M. pneumoniae-induced rash and mucositis (MIRM; n = 3/44, 7%), urticaria (n = 2, 5%), and exanthematous skin eruptions (n = 5, 11%). Two cases had ocular involvement as sole mucosal manifestation (bilateral anterior uveitis and non-purulent conjunctivitis). Cases with M. pneumoniae-induced mucocutaneous disease had longer prodromal fever (p = 0.02) and higher CRP levels (p = 0.04) than cases with M. pneumoniae CAP without skin manifestations. They were also more likely to require oxygen (p = 0.007), hospitalization (p = 0.01), and to develop long-term sequelae (p = 0.03).
Conclusion: Mucocutaneous disease occurred in one out of four cases with M. pneumoniae CAP, significantly more frequent than in CAP of other etiology. M. pneumoniae-induced mucocutaneous disease was associated with increased systemic inflammation, morbidity, and higher risk of long-term sequelae.
Zimmerdesinfektion mit UV-C-Licht bei Vancomycin-resistenten Enterokokken – eine zusätzliche Sicherheit? Eine Pilotstudie.
Aurore Portmann (Basel | CH)
Oberflächen können durch Patientinnen und Patienten, die mit multiresistenten Keimen kolonisiert oder infiziert sind, kontaminiert sein. Um nosokomiale Infektionen zu vermeiden, werden die Zimmer bei der Entlassung dieser Patienten einer Schlussdesinfektion (SD) unterzogen. Bei unzureichender SD besteht die Gefahr der Keimübertragung nachfolgenden im Zimmer stationierten Patienten.
Bringt eine UV-C-Desinfektion bei Austritt von Patienten, die mit Vancomycin-resistenten Enterokokken (VRE) kolonisiert oder infiziert sind, eine messbare Abnahme von Erregern gegenüber den Standardverfahren der SD?
Material und Methoden
Am Universitätsspital Basel wurden zwischen Oktober 2018 bis April 2019 zwanzig Zimmer nach Austritt von VRE-Patienten untersucht. Acht Abstrichstellen wurden dabei berücksichtigt: Toiletten-Brille, WC-Knopf Spülung, Abdeckung WC-Papier, Wasserhahn der Nasszelle, Boden, Patienten-Bettklingel, Schublade des Nachttisches und Klapptisch.
Die mikrobiologischen Proben wurden mittels RODAC-Abklatschplatten (Merck) und eSwab™ (COPAN) zu drei Zeitpunkten entnommen: a) vor SD, b) nach SD und vor UV-C-Desinfektion, c) nach UV-C-Desinfektion. Von den eSwab™ wurden 0,2 ml Flüssigkeit entnommen und auf CNA-Platten ausgestrichen. Abklatsch- und CNA-Platten wurden während 48 Std. bei 35°C bebrütet.
Bei Wachstum wurde je eine Subkultur auf Columbia Blut-Agar und CNA-Platten angesetzt. Eine weitere Differenzierung wurde mittels MALDI-TOF verarbeitet. Eine VITEK-Resistenzprüfung sowie eine Typisierung durch Next Generation Sequencing wurde bei allen nachgewiesenen E. faecium durchgeführt.
Insgesamt wurden 472 Proben analysiert. In einem der Zimmer konnten 8 Abklatsche zum Zeitpunkt b) nicht abgenommen werden. Die Anzahl positiver VRE-Proben betrug zu den Zeitpunkten a) 32 von 160, b) 4 von 152 und c) 0 von 160. Der exakte Test nach Fisher zeigte beim Vergleich der Ergebnisse der Zeitpunkte a) und c) p < 0.0001, respektive b) und c) p = 0.055.
In 55% (11/20) der Zimmer vor SD und in 36% (4/11) nach SD wurde VRE nachgewiesen. In Zimmern, die nach SD VRE-positiv waren, wurde VRE nach UV-C-Desinfektion zu keinem Zeitpunkt festgestellt.
Die SD mit einem Kombinationspräparat aus quartären Ammoniumverbindungen mit Aldehyd und Glutaraldehyd ist unzureichend, um VRE vollständig zu eliminieren. Eine zusätzliche Desinfektion mit UV-C scheint eine zuverlässige Methode zu sein, um die Sicherheit für die Patienten zu erhöhen.
Two Years of Viral Metagenomics in a Tertiary Diagnostics Unit: Evaluation of the First 35 Cases
Andreas Plate (Zürich | CH)
Metagenomic sequencing can capture the full spectrum of viral pathogens in a clinical specimen and has the potential to become a rapid, all-in-one solution for virus diagnostics. To date, clinical application is still in an early phase as current workflows are technical demanding and methodological limitations remain. Here, we evaluated the impact of viral metagenomics for cases analyzed over two years in a tertiary diagnostics unit.
Virome analysis was performed upon request by the treating clinician in 35 cases, where the etiology of infection remained unknown after routine diagnostic testing or the initial differential diagnosis was very broad. Clinical specimens were analyzed by high-throughput metagenomic sequencing in separate reactions for DNA and RNA viruses. Results obtained by metagenomic analyses were compared to the results and the workload of conventional routine testing.
Over two years, 55 specimens from 35 patients were tested by virus metagenomic sequencing. The main sample types were cerebrospinal fluid (29%), blood (26%) and throat swabs (11%). In the majority of the cases inflammatory central nervous system disorders like meningitis or meningoencephalitis were investigated (43%), followed by pathologies of the peri- and myocard (17%). 40% of the patients were immunocompromised. In parallel to metagenomic sequencing, conventional virus diagnostic tests were performed (mean 26 individual tests/patient). Metagenomic sequencing detected viruses in 12 cases (34%). These included viruses that were confirmed by routine diagnostics but in several cases also revealed virus infections that were not included or found in the performed routine diagnostic tests (e.g. Tick-borne encephalitis virus, Human immunodeficiency virus 1 or JC Virus).
Two years’ experience of metagenomic sequencing in a tertiary diagnostics unit demonstrated several advantages of an untargeted approach for virus diagnostics, highlighting the potential as first-line diagnostic tool.
Identifying the essentialome of Theileria-induced transformation
Marina Maurizio (Bern | CH)
Intracellular single-celled parasites belonging to the phylum of Apicomplexa are amongst the most prevalent and morbidity-causing pathogens worldwide. A striking example is Theileria, which affects millions of cattle in developing countries and has a substantial economic impact. The most medically important species are T. annulata and T. parva, which cause leukoproliferative diseases called Tropical Theileriosis and East Coast Fever, respectively. Theileria is unique in biology as it is the only eukaryotic cell known to fully transform its eukaryotic host cell. We hypothesize that there are host cell-derived factors that are required for parasite-induced transformation but dispensable for the host. To address this we generated a bovine genome-wide CRISPR/Cas9 library containing 85,155 gRNAs, targeting 21,039 protein-coding genes (4 gRNAs per gene). We will perform genome wide CRISPR/Cas9 drop out screens in Theileria-infected bovine cells and their non-infected controls to identify essential genes. We will compare the essentialome of BL20 cells (B cells derived from a calf with sporadic bovine leukosis) with TBL20 cells (BL20 infected with T. annulata). The BL20/TBL20 model is an ideal system to investigate changes induced by Theileria, as the two cell lines share the same host cell background. We have already performed a pilot screen in Cas9-expressing TaC12 cells, an adherent, macrophage-like cell line infected with T. annulata which we have studied extensively in the context of host-parasite interactions. To assess the effective representation of our bovine sgRNA library, genomic DNA was isolated from TaC12 cells 7 days after transduction with the lentiviral pool, the sgRNA cassette was amplified by PCR, and the abundance of sgRNAs was quantified by Illumina sequencing. We detected 99.96% of all sgRNAs with an average read count of 500, representing an excellent library representation at the start of our experiment. Cells were then maintained in culture with a minimal coverage of 500 for 4 weeks, and DNA harvested at multiple time points. By comparing the expression of sgRNAs at day 0 and following 12 passages, we expect to see a depletion of perturbations that lead to reduced cell fitness, allowing us to identify essential genes. Essential genes that are identified only in infected cells will then be validated using a small scale targeted sgRNA library, followed by gene ontology analysis to extract critical biochemical pathways, and identification of protein interaction networks. We expect that by identifying the essentialome of Theileria induced transformation, we may be able to develop targeted therapeutic strategies to kill the parasite while leaving the host intact. Moreover, such knowledge may be useful to genetically modify animals and generate livestock that are completely resistant to Theileria infection in the future.