Potential for autoimmune pathogenesis of Rift Valley Fever virus retinitis

Outbreak of Rift Valley Fever Retinitis in Rwanda: Novel Imaging Findings and Response to Treatment with Corticosteroids

PURPOSE

To describe the clinical and epidemiological characteristics of the first epidemic of Rift Valley Fever retinitis in Rwanda and to report novel imaging findings and a possible role for corticosteroids.

METHODS

Retrospective analysis of all patients who presented with presumed Rift Valley Fever retinitis at the Rwanda Charity Eye Hospital over a period of 4 months in 2022. Multimodal images are reviewed including optical coherence tomography, fluorescein angiography, color, infrared, red-free, and autofluorescence photography.

RESULTS

The newly identified arciform hyporeflective pattern on infrared imaging was present in 100% of patients. Out of 9 patients treated with oral corticosteroids, 7 (78%) experienced a visual acuity increase of at least 0.2 during follow-up, in comparison to only 4 (28%) out of 14 of untreated patients. Out of four patients treated with a subtenon corticosteroid injection, only one (25%) reached this threshold. Post-hoc pairwise comparison with Bonferroni correction revealed a significant difference in average visual acuity improvement (p = 0.034) between patients receiving oral corticosteroids (0.35 ± 0.07) versus no treatment (0.11 ± 0.04).

CONCLUSION

The identified arciform hyporeflective pattern on infrared imaging appears to be characteristic of Rift Valley Fever retinitis and should be known to clinicians working in endemic regions. Compared to a historical cohort and to untreated patients in this non-randomized study, there appears to be a benefit of treatment with oral corticosteroids.

Bilateral macular retinitis in patients with presumed rift valley fever from Sudan: A case series

BACKGROUND

Epidemic retinitis occurs seasonally following febrile infections in endemic regions. Rift valley fever (RVF) is endemic to Sudan, with a recent outbreak starting in 2019.

METHODS

Retrospective case series of 3 patients travelling from Sudan with post-febrile retinitis, and with a history and clinical picture suggestive of RVF retinitis.

RESULTS

The three patients were adult males with underlying medical conditions and underwent fundus fluorescein angiography that confirmed bilateral retinitis and occlusive vasculitis involving the posterior pole. Optical coherence tomography showed distortion of the macular layers. Case 2 presented 1 month following febrile illness and had retinal thinning, with optical coherence tomography angiography showing marked reduction in vessel density.

CONCLUSION

We present multimodal imaging data of three cases with presumed RVF retinitis from a recent outbreak in Sudan. The unavailability of standardized methods of testing for RVF, as is the case for most epidemic retinitis-causing pathogens, makes the diagnosis challenging.

Clinical manifestations of Rift Valley fever in humans: Systematic review and meta-analysis

BACKGROUND

Rift Valley fever (RVF) is an emerging, neglected, mosquito-borne viral zoonosis associated with significant morbidity, mortality and expanding geographical scope. The clinical signs and symptoms in humans are non-specific and case definitions vary. We reviewed and analysed the clinical manifestations of RVF in humans.

METHODS

In this systematic review and meta-analysis we searched on different dates, the Embase (from 1947 to 13th October 2019), Medline (1946 to 14th October 2019), Global Health (1910 to 15th October 2019), and Web of Science (1970 to 15th October 2019) databases. Studies published in English, reporting frequency of symptoms in humans, and laboratory confirmed RVF were included. Animal studies, studies among asymptomatic volunteers, and single case reports for which a proportion could not be estimated, were excluded. Quality assessment was done using a modified Hoy and Brooks et al tool, data was extracted, and pooled frequency estimates calculated using random effects meta-analysis.

RESULTS

Of the 3765 articles retrieved, less than 1% (32 articles) were included in the systematic review and meta-analysis. Nine RVF clinical syndromes were reported including the general febrile, renal, gastrointestinal, hepatic, haemorrhagic, visual, neurological, cardio-pulmonary, and obstetric syndromes. The most common clinical manifestations included fever (81%; 95% Confidence Interval (CI) 69-91; [26 studies, 1286 patients]), renal failure (41%; 23-59; [4, 327]), nausea (38%; 12-67; [6, 325]), jaundice (26%; 16-36; [15, 393]), haemorrhagic disease (26%; 17-36; [16, 277]), partial blindness (24%; 7-45; [11, 225]), encephalitis (21%; 11-33; [4, 327]), cough (4%; 0-17; [4, 11]), and miscarriage (54%) respectively. Death occurred in 21% (95% CI 14-29; [16 studies, 328 patients]) of cases, most of whom were hospitalised.

DISCUSSION

This study delineates the complex symptomatology of human RVF disease into syndromes. This approach is likely to improve case definitions and detection rates, impact outbreak control, increase public awareness about RVF, and subsequently inform 'one-health' policies. This study provides a pooled estimate of the proportion of RVF clinical manifestations alongside a narrative description of clinical syndromes. However, most studies reviewed were case series with small sample sizes and enrolled mostly in-patients and out-patients, and captured symptoms either sparsely or using broad category terms.

Urban risk factors for human Rift Valley fever virus exposure in Kenya

The Rift Valley fever virus (RVFV) is a zoonotic arbovirus that can also transmit directly to humans from livestock. Previous studies have shown consumption of sick animal products are risk factors for RVFV infection, but it is difficult to disentangle those risk factors from other livestock rearing activities. Urban areas have an increased demand for animal source foods, different vector distributions, and various arboviruses are understood to establish localized urban transmission cycles. Thus far, RVFV is an unevaluated public health risk in urban areas within endemic regions. We tested participants in our ongoing urban cohort study on dengue (DENV) and chikungunya (CHIKV) virus for RVFV exposure and found 1.6% (57/3,560) of individuals in two urban areas of Kenya had anti-RVFV IgG antibodies. 88% (50/57) of RVFV exposed participants also had antibodies to DENV, CHIKV, or both. Although livestock ownership was very low in urban study sites, RVFV exposure was overall significantly associated with seeing goats around the homestead (OR = 2.34 (CI 95%: 1.18-4.69, p = 0.02) and in Kisumu, RVFV exposure was associated with consumption of raw milk (OR = 6.28 (CI 95%: 0.94-25.21, p = 0.02). In addition, lack of piped water and use of small jugs (15-20 liters) for water was associated with a higher risk of RVFV exposure (OR = 5.36 (CI 95%: 1.23-16.44, p = 0.01) and this may contribute to interepidemic vector-borne maintenance of RVFV. We also investigated perception towards human vaccination for RVFV and identified high acceptance (91% (97/105) at our study sites. This study provides baseline evidence to guide future studies investigating the urban potential of RVFV and highlights the unexplored role of animal products in continued spread of RVFV.

The challenging management of Rift Valley Fever in humans: literature review of the clinical disease and algorithm proposal

Rift Valley Fever (RVF) is an emerging zoonotic arbovirus with a complex cycle of transmission that makes difficult the prediction of its expansion. Recent outbreaks outside Africa have led to rediscover the human disease but it remains poorly known. The wide spectrum of acute and delayed manifestations with potential unfavorable outcome much complicate the management of suspected cases and prediction of morbidity and mortality during an outbreak. We reviewed literature data on bio-clinical characteristics and treatments of RVF human illness. We identified gaps in the field and provided a practical algorithm to assist clinicians in the cases assessment, determination of setting of care and prolonged follow-up.

The influence of raw milk exposures on Rift Valley fever virus transmission

Rift Valley fever virus (RVFV) is a zoonotic phlebovirus that can be transmitted to humans or livestock by mosquitoes or through direct contact with contaminated bodily fluids and tissues. Exposure to bodily fluids and tissues varies by types of behaviors engaged for occupational tasks, homestead responsibilities, or use in dietary or therapeutic capacities. While previous studies have included milk exposures in their analyses, their primary focus on livestock exposures has been on animal handling, breeding, and slaughter. We analyzed data from multiple field surveys in Kenya with the aim of associating RVFV infection to raw milk exposures from common animal species. Of those with evidence of prior RVFV infection by serology (n = 267), 77.2% engaged in milking livestock compared to 32.0% for 3,956 co-local seronegative individuals (p < 0.001), and 86.5% of seropositive individuals consumed raw milk compared to 33.4% seronegative individuals (p < 0.001). Individuals who milked and also consumed raw milk had greater odds of RVFV exposure than individuals whose only contact to raw milk was through milking. Increased risks were associated with exposure to milk sourced from cows (p < 0.001), sheep (p < 0.001), and goats (p < 0.001), but not camels (p = 0.98 for consuming, p = 0.21 for milking). Our data suggest that exposure to raw milk may contribute to a significant number of cases of RVFV, especially during outbreaks and in endemic areas, and that some animal species may be associated with a higher risk for RVFV exposure. Livestock trade is regulated to limit RVFV spread from endemic areas, yet further interventions designed to fully understand the risk of RVFV exposure from raw milk are imperative.

[Tropical ophthalmology : Intraocular inflammation caused by "new" infectious pathogens and travel-related infections]

A number of "new" (emerging) infections that can also cause inflammatory eye changes are appearing and becoming increasingly important. In the past, diseases such as chikungunya, dengue fever or West Nile virus infections were endemic in tropical regions, but are now expanding worldwide and causing significant morbidity and even mortality. "Globalization" and human migration are important factors leading to the import of these infections. Climate changes are probably even more important. Increasing temperatures provide suitable conditions for new vectors, and may lead to autochthonous transmission of infectious pathogens. Diagnosis of these diseases requires not only careful assessment of medical and travel history, but also the application of specific laboratory diagnostic tests. A broad spectrum of ocular involvement has been reported, with frequent posterior segment involvement. Emerging infections should therefore be considered in the differential diagnosis of retinitis, chorioretinitis, retinal vasculitis and optic neuropathy in a patient living in or traveling back from an endemic area. Since these infections are often vector (insect) borne and effective treatments are almost uniformly lacking, prevention is at least as important as prompt diagnosis and initiation of supportive care. Here, we focus on Chikungunya, Dengue fever, Ebola fever, the West Nile virus and Rickettsioses, which frequently demonstrate ocular involvement.

Rift Valley fever virus: Unanswered questions

This mosquito-borne pathogen of humans and animals respects no international or geographic boundaries. It is currently found in parts of Africa and the Arabian Peninsula where periodic outbreaks of severe and fatal disease occur, and threatens to spread into other geographic regions. In recent years, modern molecular techniques have led to many breakthroughs deepening our understanding of the mechanisms of RVFV virulence, phylogenetics, and the creation of several next-generation vaccine candidates. Despite tremendous progress in these areas, other challenges remain in RVF disease pathogenesis, the virus life-cycle, and outbreak response preparedness that deserve our attention. Here we discuss and highlight ten key knowledge gaps and challenges in RVFV research. Answers to these key questions may lead to the development of new effective therapeutics and enhanced control strategies for this serious human and veterinary health threat.