Abdominal stab wounds with retained knife: 15 years of experience from a major trauma centre in South Africa

INTRODUCTION

This study reviews our cumulative experience with the management of patients presenting with a retained knife following an abdominal stab wound (SW).

METHODS

A retrospective study was conducted at a major trauma centre in South Africa over a 15-year period from July 2006 to December 2020 including all patients who presented with a retained knife in the abdomen following a SW.

RESULTS

A total of 42 cases were included: 37 males (93%) with a mean age of 26 years. A total of 18 knives (43%) were in the anterior abdomen and 24 were posterior abdomen. Plain radiography was performed in 88% (37/42) of cases and computed tomography was performed in 81% (34/42); 90% (38/42) underwent extraction in the operating theatre. Laparotomy was performed in 62% (26/42). Of all the laparotomies performed, 77% (20/26) were positive for intra-abdominal organ or visceral injury. Overall morbidity was 31%. There were two mortalities (5%). Laparotomy was less commonly required for the posterior abdomen (33% (8/24) vs 100% (18/18), p<0.001). For retained knives in the anterior abdomen, 72% (13/18) of the laparotomies were positive for intra-abdominal organ or visceral injury. For the posterior abdomen, 7 of the 8 (88%) were positive for intra-abdominal organ or visceral injury. There were no differences in the need for intensive care unit admission, length of hospital stay, morbidities or mortalities.

CONCLUSIONS

Uncontrolled extraction of a retained knife in the abdomen outside of the operating theatre must be avoided. Retained knives in the anterior abdomen usually require formal laparotomy, but this is generally not required for posterior abdomen.

Rehabilitation for people wearing offloading devices for diabetes-related foot ulcers: a systematic review and meta-analyses

BACKGROUND

Offloading devices improve healing of diabetes-related foot ulcers (DFUs) but they can limit mobilisation. Rehabilitation during or after removal of these devices may promote physical activity in a population at risk of poor health outcomes for which inactivity is a reversible risk factor.

METHODS

This systematic review examined the effectiveness of rehabilitation interventions to promote physical activity during and/or after wearing an offloading device to treat diabetes-related foot ulcers. Searches using MESH terms and free-text combinations: 'foot ulcer', 'diabetic foot', 'casts, surgical', 'orthotic devices' were applied to MEDLINE, Embase, The Cochrane Library and clinical trial registers for randomised and observational studies published to September 2022. Methodological quality assessment of included studies was undertaken using the Cochrane Risk of Bias (RoB 2.0) and Risk of Bias In Non-randomised studies of Interventions (ROBINS-I) tools.

RESULTS

Of 3332 records identified, eight studies (441 participants), four clinical trials and four cohort studies, were included. None delivered or tested a structured rehabilitation programme, but all reported physical activity outcomes during or after device use. People wearing non-removable total contact casts were less active than those wearing devices (SMD -0.45; 95% CI - 0.87 to - 0.04; p = 0.03; I² 56%; 4 trials). Diabetes-related foot ulcers in people wearing total contact casts were more likely to heal compared to removable devices at 12 weeks (OR 2.69; 95% CI 0.97 to 7.45; p = 0.06; I² = 64%; 4 trials) and 20 weeks (OR 2.35; 95% CI 0.95 to 5.82; p = 0.07; I² = 65%; 4 trials).

CONCLUSIONS

Despite physical activity being low throughout off-loading treatment, no studies have specifically tested rehabilitation. There is a need to investigate the clinical and cost-effectiveness of rehabilitation programmes in this population. High quality trials are needed to provide robust evidence to support to rehabilitation after DFU treatment.

An audit of trauma laparotomy in children and adolescents highlights the role of damage control surgery and the need for a trauma systems approach to injury in this vulnerable population

BACKGROUND: This study reviews the indications and outcome of emergency laparotomy for paediatric trauma in a South African trauma centre. METHODS: This was a retrospective study of all children less than 18 years of age who underwent an emergency laparotomy for trauma between December 2012 and October 2020 at Grey's Hospital in Pietermaritzburg. RESULTS: During the eight-year period under review, a total of136 children of which 107 were male underwent a laparotomy for trauma. The median age was 14 years. There were 80 (57.1%) blunt mechanisms, and the rest were penetrating mechanisms. A total of 46 (33%) patients required ICU admission. Thirty-four patients developed a complication. These included nine cases of pneumonia, one case of renal failure, two patients developed abdominal collections, three wound-related complications, three neurological complications and one miscellaneous complication. There were seven (5%) deaths. The penetrating cohort were older than the blunt cohort. Solid viscera were more likely to be injured in the blunt cohort and hollow viscera more likely in the penetrating cohort. A total of 16 (11%) patients underwent damage control surgery (DCS). Of this cohort, there were three female children. Six sustained blunt trauma and ten penetrating trauma. A total of six (37%) of these children died. CONCLUSION: Emergency laparotomy for trauma in children is not infrequent in Pietermaritzburg and there is a high incidence of penetrating trauma in this cohort. The response to increased degrees of physiological derangement is the application of DCS. Ongoing efforts to develop and strengthen a paediatric trauma service appear to be justified.

Management of penetrating thoracic trauma with retained knife blade: 15-year experience from a major trauma centre in South Africa

INTRODUCTION

This study reviews our experience with the management a retained knife in the setting of thoracic stab wounds.

METHODS

A retrospective study was conducted at a major trauma in South Africa over a 15-year period from January 2004 to December 2018.

RESULTS

There were 40 patients, of whom 37 were males (93%). Median age was 24 years; 78% of cases (31 of 40) were a retained knife and 23% (9 of 40) were a retained blade. The locations of the stab wounds were 19 (48%) anterior and 21 (53%) posterior. Plain x-ray was performed in 85% (34) of patients and computed tomography angiography was performed in 85% (34). Six patients had haemodynamic instability and were expedited to the operating room without further imaging. Three of these had cardiac tamponade and three a massive haemothorax. Simple extraction and wound exploration were performed in 58% (23 of 40) of cases and the remaining 43% (17 of 40) required operative exploration and extraction. The operative approach was anterolateral thoracotomy in nine cases, posterolateral thoracotomy in four and median sternotomy in three cases. One patient required extraction and concurrent vertebral laminectomy due to cord compression. Twelve patients (30%) experienced complications (nine wound sepsis and three hospital-acquired pneumonia). There was one mortality (3%). The median length of hospital stay was 6 days.

CONCLUSION

Uncontrolled extraction of a retained thoracic knife outside the operating room must be avoided. An unstable patient should proceed directly for operative exploration. For stable patients, cross-sectional imaging will allow for planned extraction in operating room.

"Watch Me Grow- Electronic (WMG-E)" surveillance approach to identify and address child development, parental mental health, and psychosocial needs: study protocol

Background

The COVID-19 pandemic and the associated economic recession has increased parental psychosocial stress and mental health challenges. This has adversely impacted child development and wellbeing, particularly for children from priority populations (culturally and linguistically diverse (CALD) and rural/regional communities) who are at an already increased risk of health inequality. The increased mental health and psychosocial needs were compounded by the closure of in-person preventive and health promotion programs resulting in health organisations embracing technology and online services. Watch Me Grow- Electronic (WMG-E) – developmental surveillance platform- exemplifies one such service.

WMG-E was developed to monitor child development and guide parents towards more detailed assessments when risk is identified. This Randomised Controlled Trial (RCT) aims to expand WMG-E as a digital navigation tool by also incorporating parents’ mental health and psychosocial needs. Children and families needing additional assessments and supports will be electronically directed to relevant resources in the ‘care-as-usual’ group. In contrast, the intervention group will receive continuity of care, with additional in-person assessment and ‘warm hand over’ by a ‘service navigator’ to ensure their needs are met.

Methods

Using an RCT we will determine: (1) parental engagement with developmental surveillance; (2) access to services for those with mental health and social care needs; and (3) uptake of service recommendations. Three hundred parents/carers of children aged 6 months to 3 years (recruited from a culturally diverse, or rural/regional site) will be randomly allocated to the ‘care-as-usual’ or ‘intervention’ group. A mixed methods implementation evaluation will be completed, with semi-structured interviews to ascertain the acceptability, feasibility and impact of the WMG-E platform and service navigator.

Conclusions

Using WMG-E is expected to: normalise and de-stigmatise mental health and psychosocial screening; increase parental engagement and service use; and result in the early identification and management of child developmental needs, parental mental health, and family psychosocial needs. If effective, digital solutions such as WMG-E to engage and empower parents alongside a service navigator for vulnerable families needing additional support, will have significant practice and policy implications in the pandemic/post pandemic period.

Trial registration

The trial (Protocol No. 1.0, Version 3.1) was registered with ANZCTR (registration number: ACTRN12621000766819) on July 21st, 2021 and reporting of the trial results will be according to recommendations in the CONSORT Statement.

Automated conversational agents for post-intervention follow-up: a systematic review

BACKGROUND

Advances in natural language processing and other machine learning techniques have led to the development of automated agents (chatbots) that mimic human conversation. These systems have mainly been used in commercial settings, and within medicine, for symptom checking and psychotherapy. The aim of this systematic review was to determine the acceptability and implementation success of chatbots in the follow-up of patients who have undergone a physical healthcare intervention.

METHODS

A systematic review of MEDLINE, MEDLINE In-process, EMBASE, PsychINFO, CINAHL, CENTRAL and the grey literature using a PRISMA-compliant methodology up to September 2020 was conducted. Abstract screening and data extraction were performed in duplicate. Risk of bias and quality assessments were performed for each study.

RESULTS

The search identified 904 studies of which 10 met full inclusion criteria: three randomised control trials, one non-randomised clinical trial and six cohort studies. Chatbots were used for monitoring after the management of cancer, hypertension and asthma, orthopaedic intervention, ureteroscopy and intervention for varicose veins. All chatbots were deployed on mobile devices. A number of metrics were identified and ranged from a 31 per cent chatbot engagement rate to a 97 per cent response rate for system-generated questions. No study examined patient safety.

CONCLUSION

A range of chatbot builds and uses was identified. Further investigation of acceptability, efficacy and mechanistic evaluation in outpatient care pathways may lend support to implementation in routine clinical care.

Traumatic renal injury: Five-year experience at a major trauma centre in South Africa

BACKGROUND

This study is intended to assess the current optimal management of traumatic renal injuries (TRIs), with a focus on high-grade and penetrating injuries.

METHODS

The Pietermaritzburg Metropolitan Trauma Service registry was interrogated retrospectively for patients managed for TRI between 1 January 2012 and 31 December 2016.

RESULTS

Of 13,315 inured patients treated by the PMTS, 223 (1.7%) had TRIs with an incidence of 1.5 per 100,000 population per year. The majority were males between 20 and 39 years of age. The distribution of mechanism of injury was 56.1% (n = 125) blunt and 43.9% (n = 98) penetrating trauma with no association between mechanism and grade of injury. Penetrating trauma was associated with hollow viscus and diaphragm injuries and blunt trauma with solid organ injuries. A total of 118 patients (52.9%) were managed non-operatively, 60 (26.9%) were not explored at operation, 27 (12.1%) underwent initial nephrectomy and 8 (3.6%) underwent renorraphy. Low-grade injuries (AAST I and II) and high-grade injuries (AAST III-V) were managed without renal intervention (non-operatively or not explored at laparotomy for associated injuries) in 88.7% (n = 87) and 72.0% (n = 91) of cases respectively. Blunt and penetrating injuries were managed without renal intervention in 87.9% (n = 109) and 70% (n = 69) of cases respectively. The initial nephrectomy rate was 1% (n = 1) and 20.6% (n = 26) for low- and high-grade injuries respectively, and 6.5% (n = 8) and 19% (n = 19) for blunt and penetrating injuries respectively. High grade (AAST III-V) injury (OR 14.94; 95% CI 3.36 - 66.34; p<0.001), penetrating mechanism (OR 4.99; 95% CI 1.98 - 12.52; p = 0.001) and metabolic acidosis (OR 2.73; 95% CI 1.04 - 7.20; p = 0.042) were significant risk factors for nephrectomy. Four patients (1.8%) underwent ureteral stent insertion and 2 (0.9%) underwent embolisation. The failure rate of initial non-operative management was 1.1%. The mortality rate was 8.1% (n = 18), but no patients with solitary renal injuries died.

CONCLUSION

Even in high-grade injuries and penetrating trauma, the majority of patients with TRI can be managed non-operatively or with the assistance of endourological or endovascular techniques, with good outcomes. Risk factors for nephrectomy include the presence of high-grade injuries, penetrating trauma and metabolic acidosis on presentation.

Cost-effectiveness of negative-pressure wound therapy in adults with severe open fractures of the lower limb: evidence from the WOLLF randomized controlled trial

Aims

The aim of this study was to estimate the cost-effectiveness of negative-pressure wound therapy (NPWT) in comparison with standard wound management after initial surgical wound debridement in adults with severe open fractures of the lower limb.

Patients and Methods

An economic evaluation was conducted from the perspective of the United Kingdom NHS and Personal Social Services, based on evidence from the 460 participants in the Wound Management of Open Lower Limb Fractures (WOLLF) trial. Economic outcomes were collected prospectively over the 12-month follow-up period using trial case report forms and participant-completed questionnaires. Bivariate regression of costs (given in £, 2014 to 2015 prices) and quality-adjusted life-years (QALYs), with multiple imputation of missing data, was conducted to estimate the incremental cost per QALY gained associated with NPWT dressings. Sensitivity and subgroup analyses were undertaken to assess the impacts of uncertainty and heterogeneity, respectively, surrounding aspects of the economic evaluation.

Results

The base case analysis produced an incremental cost-effectiveness ratio of £267 910 per QALY gained, reflecting higher costs on average (£678; 95% confidence interval (CI) -£1082 to £2438) and only marginally higher QALYS (0.002; 95% CI -0.054 to 0.059) in the NPWT group. The probability that NPWT is cost-effective in this patient population did not exceed 27% regardless of the value of the cost-effectiveness threshold. This result remained robust to several sensitivity and subgroup analyses.

Conclusion

This trial-based economic evaluation suggests that NPWT is unlikely to be a cost-effective strategy for improving outcomes in adult patients with severe open fractures of the lower limb. Cite this article: Bone Joint J 2019;101-B:1392–1401.

Adherence to Point-of-Use Water Treatment over Short-Term Implementation: Parallel Crossover Trials of Flocculation-Disinfection Sachets in Pakistan and Zambia

The health benefits of point-of-use (POU) water treatment can only be realized through high adherence: correct, consistent, and sustained use. We conducted parallel randomized, longitudinal crossover trials measuring short-term adherence to two single-use flocculant-disinfectant sachets in Pakistan and Zambia. In both trials, adherence declined sharply for both products over the eight week surveillance periods, with overall lower adherence to both products in Zambia. There was no significant difference in adherence between the two products. Estimated median daily production of treated water dropped over the crossover period from 2.5 to 1.4 L person^-1 day^-1 (46% decline) in Pakistan and from 1.4 to 1.1 L person^-1 day^-1 (21% decline) in Zambia. The percentage of surveillance points with detectable total chlorine in household drinking water declined from 70% to 49% in Pakistan and rose marginally from 28% to 30% in Zambia. The relatively low and decreasing adherence observed in this study suggests that these products would have provided little protection from waterborne disease risk in these settings. Our findings underscore the challenge of achieving high adherence to POU water treatment, even under conditions of short-term adoption with intensive follow-up.

Systematic review of management of chronic pain after surgery

Background

Pain present for at least 3 months after a surgical procedure is considered chronic postsurgical pain (CPSP) and affects 10–50 per cent of patients. Interventions for CPSP may focus on the underlying condition that indicated surgery, the aetiology of new‐onset pain or be multifactorial in recognition of the diverse causes of this pain. The aim of this systematic review was to identify RCTs of interventions for the management of CPSP, and synthesize data across treatment type to estimate their effectiveness and safety.

Methods

MEDLINE, Embase, PsycINFO, CINAHL and the Cochrane Library were searched from inception to March 2016. Trials of pain interventions received by patients at 3 months or more after surgery were included. Risk of bias was assessed using the Cochrane risk‐of‐bias tool.

Results

Some 66 trials with data from 3149 participants were included. Most trials included patients with chronic pain after spinal surgery (25 trials) or phantom limb pain (21 trials). Interventions were predominantly pharmacological, including antiepileptics, capsaicin, epidural steroid injections, local anaesthetic, neurotoxins, N‐methyl‐d‐aspartate receptor antagonists and opioids. Other interventions included acupuncture, exercise, postamputation limb liner, spinal cord stimulation, further surgery, laser therapy, magnetic stimulation, mindfulness‐based stress reduction, mirror therapy and sensory discrimination training. Opportunities for meta‐analysis were limited by heterogeneity. For all interventions, there was insufficient evidence to draw conclusions on effectiveness.

Conclusion

There is a need for more evidence about interventions for CPSP. High‐quality trials of multimodal interventions matched to pain characteristics are needed to provide robust evidence to guide management of CPSP.

Flimsy evidence base

Mipsagargin, a novel thapsigargin-based PSMA-activated prodrug: results of a first-in-man phase I clinical trial in patients with refractory, advanced or metastatic solid tumours

Background:

Mipsagargin (G-202; (8-O-(12-aminododecanoyl)-8-O-debutanoyl thapsigargin)-Asp-γ-Glu-γ-Glu-γ-GluGluOH)) is a novel thapsigargin-based targeted prodrug that is activated by PSMA-mediated cleavage of an inert masking peptide. The active moiety is an inhibitor of the sarcoplasmic/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) pump protein that is necessary for cellular viability. We evaluated the safety of mipsagargin in patients with advanced solid tumours and established a recommended phase II dosing (RP2D) regimen.

Methods:

Patients with advanced solid tumours received mipsagargin by intravenous infusion on days 1, 2 and 3 of 28-day cycles and were allowed to continue participation in the absence of disease progression or unacceptable toxicity. The dosing began at 1.2 mg m⁻² and was escalated using a modified Fibonacci schema to determine maximally tolerated dose (MTD) with an expansion cohort at the RP2D. Plasma was analysed for mipsagargin pharmacokinetics and response was assessed using RECIST criteria.

Results:

A total of 44 patients were treated at doses ranging from 1.2 to 88 mg m⁻², including 28 patients in the dose escalation phase and 16 patients in an expansion cohort. One dose-limiting toxicity (DLT; Grade 3 rash) was observed in the dose escalation portion of the study. At 88 mg m⁻², observations of Grade 2 infusion-related reaction (IRR, 2 patients) and Grade 2 creatinine elevation (1 patient) led to declaration of 66.8 mg m⁻² as the recommended phase II dose (RP2D). Across the study, the most common treatment-related adverse events (AEs) were fatigue, rash, nausea, pyrexia and IRR. Two patients developed treatment-related Grade 3 acute renal failure that was reversible during the treatment-free portion of the cycle. To help ameliorate the IRR and creatinine elevations, a RP2D of 40 mg m⁻² on day 1 and 66.8 mg m⁻² on days 2 and 3 with prophylactic premedications and hydration on each day of infusion was established. Clinical response was not observed, but prolonged disease stabilisation was observed in a subset of patients.

Conclusions:

Mipsagargin demonstrated an acceptable tolerability and favourable pharmacokinetic profile in patients with solid tumours.

Protein interaction networks at the host-microbe interface in Diaphorina citri, the insect vector of the citrus greening pathogen

The Asian citrus psyllid (Diaphorina citri) is the insect vector responsible for the worldwide spread of 'Candidatus Liberibacter asiaticus' (CLas), the bacterial pathogen associated with citrus greening disease. Developmental changes in the insect vector impact pathogen transmission, such that D. citri transmission of CLas is more efficient when bacteria are acquired by nymphs when compared with adults. We hypothesize that expression changes in the D. citri immune system and commensal microbiota occur during development and regulate vector competency. In support of this hypothesis, more proteins, with greater fold changes, were differentially expressed in response to CLas in adults when compared with nymphs, including insect proteins involved in bacterial adhesion and immunity. Compared with nymphs, adult insects had a higher titre of CLas and the bacterial endosymbionts Wolbachia, Profftella and Carsonella. All Wolbachia and Profftella proteins differentially expressed between nymphs and adults are upregulated in adults, while most differentially expressed Carsonella proteins are upregulated in nymphs. Discovery of protein interaction networks has broad applicability to the study of host-microbe relationships. Using protein interaction reporter technology, a D. citri haemocyanin protein highly upregulated in response to CLas was found to physically interact with the CLas coenzyme A (CoA) biosynthesis enzyme phosphopantothenoylcysteine synthetase/decarboxylase. CLas pantothenate kinase, which catalyses the rate-limiting step of CoA biosynthesis, was found to interact with a D. citri myosin protein. Two Carsonella enzymes involved in histidine and tryptophan biosynthesis were found to physically interact with D. citri proteins. These co-evolved protein interaction networks at the host-microbe interface are highly specific targets for controlling the insect vector responsible for the spread of citrus greening.

Assessment of chronic post-surgical pain after knee replacement: development of a core outcome set

Background

Approximately 20% of patients experience chronic post-surgical pain (CPSP) after total knee replacement (TKR). There is scope to improve assessment of CPSP after TKR, and this study aimed to develop a core outcome set.

Methods

Eighty patients and 43 clinicians were recruited into a three-round modified Delphi study. In Round 1, participants were presented with 56 pain features identified from a systematic review, structured interviews with patients and focus groups with clinicians. Participants assigned importance ratings, using a 1–9 scale, to individual pain features; those features rated as most important were retained in subsequent rounds. Consensus that a pain feature should be included in the core outcome set was defined as the feature having a rating of 7–9 by ≥70% of both panels (patients and clinicians) and 1–3 by ≤15% of both panels or rated as 7–9 by ≥90% of one panel.

Results

Round 1 was completed by 71 patients and 39 clinicians, and Round 3 by 62 patients and 33 clinicians. The final consensus was that 33 pain features were important. These were grouped into an 8-item core outcome set comprising: pain intensity, pain interference with daily living, pain and physical functioning, temporal aspects of pain, pain description, emotional aspects of pain, use of pain medication, and improvement and satisfaction with pain relief.

Conclusions

This core outcome set serves to guide assessment of CPSP after TKR. Consistency in assessment can promote standardized reporting and facilitate comparability between studies that address a common but understudied type of CPSP.

Preliminary evaluation of a nonanal lure for collection of gravid Culex quinquefasciatus

Gravid traps are important tools for disease monitoring and for research on mosquito ovipositional behavior. Two experiments were conducted to evaluate a 2% nonanal lure in gravid mosquito traps in Ifakara, Tanzania. The 1st experiment focused on whether water was needed in the pan below the trap for the nonanal lure to be effective. There was no significant difference between the numbers of gravid females of Culex quinquefasciatus collected in traps using a nonanal lure either with or without water. The 2nd experiment compared the lure, without water, to a grass infusion and a blank trap, without water or attractant. Significantly more mosquitoes were collected in traps with grass infusion than in traps with the other attractants, which were not significantly different from each other. Although more mosquitoes were collected in traps with grass infusion, substantial numbers were also collected in traps with the nonanal lure and unbaited traps.

The eXpeRience registry: the 'real-world' effectiveness of omalizumab in allergic asthma

Omalizumab has demonstrated therapeutic benefits in controlled clinical trials. Evaluation of outcomes in real-world clinical practice is needed to provide a complete understanding of the benefits of omalizumab treatment. eXpeRience was a 2-year, international, single-arm, open-label, observational registry that evaluated real-world effectiveness, safety and use of omalizumab therapy in 943 patients with uncontrolled persistent allergic asthma. Effectiveness variables (physician's Global Evaluation of Treatment Effectiveness [GETE], and change from baseline in exacerbation rate, symptoms, rescue medication use, and oral corticosteroid [OCS] use) were evaluated at pre-specified time-points. Safety data were also recorded. By physician's GETE, 69.9% of patients were responders to omalizumab after 16 (±1) weeks. The proportion of patients with no clinically significant exacerbations increased from 6.8% during the 12-month pre-treatment period to 54.1% and 67.3% at Months 12 and 24, respectively. Symptoms and rescue medication use at Month 24 were reduced by >50% from baseline. Maintenance OCS use was lower at Month 24 (14.2%) compared with Month 12 (16.1%) and baseline (28.6%). Overall, omalizumab had an acceptable safety profile. The results from eXpeRience indicate that omalizumab was associated with improvements in outcomes in patients with uncontrolled persistent allergic asthma; these improvements were consistent with the results of clinical trials.

Evaluation of a nonanal-trimethylamine lure for collection of Culex quinquefasciatus (Diptera: Culicidae) in gravid traps

Gravid traps are useful tools for monitoring vector-borne pathogens in mosquitoes, particularly for those pathogens transmitted by Culex quinquefasciatus Say. One of the primary challenges in the use of gravid traps is the necessity of the inclusion of an oviposition attractant, usually an infusion of organic material, which changes in attractiveness over time. However, a standardized lure, using nonanal and trimethylamine (N + TMA), has been developed and is commercially available. The N + TMA lure was tested against grass infusion and tap water in Tanzania, where Cx. quinquefasciatus is a vector of lymphatic filariasis. Traps baited with grass infusion collected significantly more mosquitoes than N + TMA-baited traps, which collected significantly more than traps baited with tap water. The advantages and disadvantages of the standardized lure are discussed.

Effect of the volume of organic infusion used in gravid traps for collecting Culex quinquefasciatus (Diptera: Culicidae)

Traps that selectively collect gravid mosquitoes have advantages over other collection methods for the purpose of disease surveillance: they trap mosquitoes with a higher probability of carrying disease as they have blood fed on at least one occasion. Gravid traps typically use infusions of organic material to attract gravid mosquitoes, particularly Culex quinquefasciatus (Say). These infusions are heavy and have an unpleasant odor, presenting logistical difficulties for disease monitoring programs. Typically, gravid traps use 4 liters of infusion. The present trial compared the responses of gravid female mosquitoes to 2 and 4 liters of infusion to see if equivalent numbers of mosquitoes could be collected using the smaller volume. In an attempt to better understand the effects of volume of infusion on mosquito oviposition behavior, egg laying on the two volumes was also monitored. There was a significant difference between the mean numbers of egg rafts laid on 2 and 4 liters of infusion. However, the mean numbers of gravid Cu. quinquefasciatus collected in gravid traps with 2 and 4 liters were not significantly different. The results indicate that 2 liters can be used instead of 4 liters for gravid trapping, significantly reducing the cost and logistical difficulties associated with such efforts. The behavioral responses of gravid females to different volumes are also discussed.