Use of whole blood dried on filter paper for detection and genotyping of measles virus

Measles incidence in South Africa: a six-year review, 2015-2020

In 2012 the World Health Organization (WHO) aimed to eliminate measles in five regions by 2020. This retrospective descriptive study reviewed measles surveillance data in South Africa for the period 2015-2020 to document the epidemiology of measles and the progress made towards meeting the 2020 measles elimination goal.A total of 22,578 specimens were tested over the period 2015-2020 yielding 401 (1.8%) confirmed measles cases, 321 (1.4%) compatible and 21,856 (96.8%) discarded cases. The most affected age group was 0-4 year olds. At the provincial level, South Africa achieved adequate surveillance, defined as more than two cases of febrile rash notified annually per 100 000 popoulation, except for KwaZulu-Natal and Limpopo in 2020, probably due to COVID-19 lockdown restrictions. Of confirmed cases, only 26% were vaccinated, 3% were too young to receive vaccines, 5% were not vaccinated, and 65% had unknown vaccination status. Measles vaccine effectiveness amongst 1-4 year olds was 80%. Using the standard case definition, South Africa achieved the measles elimination target of less than one case per one million nationally in years 2015, 2016 and 2020. The years 2017 to 2019 had incidence rates exceeding one per million nationally. Using a narrow case definition, that excluded positive rubella cases, improved the indicators with only the year 2017 having an incidence rate of more than one per million.South Africa displays intermittent measles outbreaks approximately six-yearly interspersed by inter-epidemic periods in which the country meets measles elimination targets. Intense effort is needed to increase the vaccine coverage to avoid periodic outbreaks. Enhanced molecular testing of each case will be required as measles incidence declines regionally.

Dried fluid spots for peste des petits ruminants virus load evaluation allowing for non-invasive diagnosis and genotyping

BACKGROUND

Active surveillance of peste des petits ruminants (PPR) should ease prevention and control of this disease widely present across Africa, Middle East, central and southern Asia. PPR is now present in Turkey at the gateway to the European Union. In Bangladesh, the diagnosis and genotyping of PPR virus (PPRV) may be hampered by inadequate infrastructures and by lack of proper clinical material, which is often not preserved under cold chain up to laboratories. It has been shown previously that Whatman® 3MM filter paper (GE Healthcare, France) preserves the nucleic acid of PPRV for at least 3 months at 32°C.

RESULTS

In this study, we demonstrate the performances of filter papers for archiving RNA from local PPRV field isolates for further molecular detection and genotyping of PPRV, at -70°C combined with ambient temperature, for periods up to 16 months. PPR-suspected live animals were sampled and their blood and nasal swabs were applied on filter papers then air dried. Immediately after field sampling, RT-PCR amplifying a 448-bp fragment of the F gene appeared positive for both blood and nasal swabs when animals were in febrile stage and only nasal swabs were detected positive in non-febrile stage. Those tested positive were monitored by RT-PCR up to 10 months by storage at -70°C. At 16 months, using real time RT-PCR adapted to amplify the N gene from filter paper, high viral loads could still be detected (~2 x 10(7) copy numbers), essentially from nasal samples. The material was successfully sequenced and a Bayesian phylogenetic reconstruction achieved adequate resolution to establish temporal relationships within or between the geographical clusters of the PPRV strains.

CONCLUSIONS

This clearly reveals the excellent capacity of filter papers to store genetic material that can be sampled using a non-invasive approach.

Dried-blood spots: a cost-effective field method for the detection of Chikungunya virus circulation in remote areas

BACKGROUND

In 2005, there were outbreaks of febrile polyarthritis due to Chikungunya virus (CHIKV) in the Comoros Islands. CHIKV then spread to other islands in the Indian Ocean: La Réunion, Mauritius, Seychelles and Madagascar. These outbreaks revealed the lack of surveillance and preparedness of Madagascar and other countries. Thus, it was decided in 2007 to establish a syndrome-based surveillance network to monitor dengue-like illness.

OBJECTIVE

This study aims to evaluate the use of capillary blood samples blotted on filter papers for molecular diagnosis of CHIKV infection. Venous blood samples can be difficult to obtain and the shipment of serum in appropriate temperature conditions is too costly for most developing countries.

METHODOLOGY AND PRINCIPAL FINDINGS

Venous blood and dried-blood blotted on filter paper (DBFP) were collected during the last CHIKV outbreak in Madagascar (2010) and as part of our routine surveillance of dengue-like illness. All samples were tested by real-time RT-PCR and results with serum and DBFP samples were compared for each patient. The sensitivity and specificity of tests performed with DBFP, relative to those with venous samples (defined as 100%) were 93.1% (95% CI:[84.7-97.7]) and 94.4% (95% CI:[88.3-97.7]), respectively. The Kappa coefficient 0.87 (95% CI:[0.80-0.94]) was excellent.

CONCLUSION

This study shows that DBFP specimens can be used as a cost-effective alternative sampling method for the surveillance and monitoring of CHIKV circulation and emergence in developing countries, and probably also for other arboviruses. The loss of sensitivity is insignificant and involved a very small number of patients, all with low viral loads. Whether viruses can be isolated from dried blood spots remains to be determined.

The use of oral fluid samples spotted on filter paper for the detection of measles virus using nested rt-PCR

Measles is the leading cause of death in infants, although a vaccine is available for its prevention. At this stage of measles elimination and eradication, it is so important to confirm clinically diagnosed measles cases in the laboratory but, developing countries have troubles in collecting and maintaining the cold chain of the specimens while transporting them to the laboratories. Therefore, filter papers are good candidates for simplification of specimen collection and transportation. In this research, the effects of the temperature, at which the dried specimens were kept, and the time duration the dried specimens were kept before being tested, were studied. Since there were not enough patients' oral fluid samples available, a nested reverse transcriptase PCR (RT-PCR) that detected measles virus (MV) from dried filter papers was set up using MV infected cells diluted in sterile phosphate-buffered saline (PBS). Dried specimens were stored at -25°C, 4°C, and room temperature for 1 day, 1, 2, and 3 weeks before being tested. This method was then applied to filter paper oral fluids collected from nine clinically diagnosed measles patients in Iran in 2010 which were tested after being kept at room temperature for 1 day, 1 and 3 weeks after preparation. The results showed that dried oral fluids on filter papers are reliable specimens for the detection of MV RNA using nested RT-PCR, but the nested RT-PCR results of low titer viruses dried onto filter papers are not reproducible and reliable.

Long-term storage at tropical temperature of dried-blood filter papers for detection and genotyping of RNA and DNA viruses by direct PCR

In tropical countries the diagnosis of viral infections of humans or animals is often hampered by the lack of suitable clinical material and the necessity to maintain a cold chain for sample preservation up to the laboratory. This study describes the use of filter papers for rapid sample collection, and the molecular detection and genotyping of viruses when stored over long periods at elevated temperatures. Infected blood was collected on filter papers, dried and stored at different temperatures (22, 32 and 37 degrees C) for various periods (up to 9 months). Two animal viruses, African swine fever, a large double-stranded DNA virus and Peste des Petits Ruminants, a negative single-stranded RNA virus, were used to validate the method. Filter papers with dried blood containing virus or control plasmid DNA were cut in small 5mm(2) pieces and added directly to the PCR tube for conventional PCR. Nucleic acid from both viruses could still be detected after 3 months at 32 degrees C. Moreover, the DNA virus could be detected at least 9 months after conservation at 37 degrees C. PCR products obtained from the filter papers were sequenced and phylogenetic analysis carried out. The results were consistent with published sequences, demonstrating that this method can be used for virus genotyping.

Molecular and serological diagnosis of Chikungunya virus infection

INTRODUCTION

In 2005-2006, during the Chikungunya virus outbreak in La Réunion (Indian Ocean), we urgently established the molecular and serological methods for the diagnosis of Chikungunya virus (CHIKV) from various types of samples.

METHODS

CHIKV RNA was detected using a highly sensitive real-time RT PCR assay. A co-extracted and co-amplified internal control RNA was used to identify RT PCR inhibitors. Depending on their nature samples were pretreated before nucleic acid extraction. Viral loads were measured using a synthetic RNA calibrator. CHIKV immunoglobulin (Ig) G and M antibodies were detected by ELISA either from sera or from blood absorbed on filter paper.

RESULTS

CHIKV RNA was found in various types of samples such as plasma, cerebrospinal fluid, and placenta, but was not found in some samples including maternal milk and synovial samples. Detection of IgG from filter paper absorbed blood is specific and sensitive. Routine data showed that maternally transferred IgG and naturally acquired IgM persist at least 12 and 18 months, respectively.

DISCUSSION

The techniques enabled the diagnosis of chikungunya in known and newly described forms of the disease. They are used for routine diagnosis and large scale surveys.

Comparison of available methods to elute serum from dried blood spot samples for measles serology

Six existing protocols for the extraction of serum from blood spots dried onto filter paper were compared. Assessment criteria included: detection of measles IgM and IgG by the Dade Behring Enzygnost immunoassays, volumes of recovered eluates, reproducibility, processing time and throughput, difficulty of protocol, equipment required, safety and estimated costs. Detection of measles IgM in eluates obtained by four of these protocols was as in serum, and significant differences were only observed in eluates from the two remaining protocols (p < 0.05). Significant differences were found between extraction protocols regarding measles-specific IgG detection when an IgG indeterminate DBS was analyzed (p < 0.05), but not when an IgG positive and negative DBS were studied. Sufficient eluate volumes were recovered for testing in the IgM Behring assay following all protocols but two. Sufficient eluate was recovered for testing in the IgG Behring assay following all six protocols. While all protocols were relatively easy to perform, only two protocols required less than 2h for completion. In general, compared protocols performed well on the extraction of antibodies from DBS for serology with differences being observed with eluate volume recovery, turn around time, required equipment and cost. An easy-to-implement protocol is proposed for the rapid extraction of serum for measles/rubella serology in outbreak situations for use in the World Health Organization Global Measles and Rubella Laboratory Network.

Measles virus genotype circulation in Spain after implementation of the national measles elimination plan 2001-2003

Molecular characterization of measles virus is important for disease surveillance and for monitoring elimination of the virus throughout the world. Furthermore, knowledge of genotype distribution in as many countries as possible, is useful for tracing the origin of a strain, especially in countries without endemic measles disease, where most cases are imported. Data on genotypes circulating in Spain from 1970 to 1997 showed the prevalence of genotypes C1, C2, and D6, with subsequent replacement of each other. After the establishment of the Spanish Measles Elimination Plan, genotyping with a new retrotranscriptase polymerase chain reaction (RT-PCR) was undertaken directly on 92 specimens, corresponding to 90 patients, which were positive for measles by a different diagnostic RT-PCR. Genotypes B3, D4, D8, A, C2, H1, and D7 were found in different autonomous communities (Madrid, Balearic Islands, Valencia Community, Extremadura, Andalusia, Canary Islands and Murcia) between 2001 and 2003 with none of these genotypes being prevalent. After the introduction of the vaccine in 1978, the incidence of the disease decreased from 150,000 cases in 1977 to 64 in 2002. This could be the reason for the change observed in the pattern of measles genotype circulation, since this pattern was reported in countries at an advanced stage of eradication of measles. This report considers that Spain is on the way to eradicating measles.