Field Stain Research Articles

A review of loiasis and its vectors in Gabon.

Loiasis colloquially known as tropical eye worm is a neglected tropical helminthic disease that affects the rural poor population of Gabon. A systematic review of 51 documents (45 peer reviewed papers and six dissertations) over four decades has documented many knowledge gaps on loiasis and its vectors. Higher prevalence and high microfilaremia is typical wherever Chrysops vectors occur. The two main vectors were C. silacea and C. dimidiata along with the savanna species C. longicornis. The two main vectors were only caught around forested national parks at low density (<1 Chrysops per trap per day). Chrysops longicornis was trapped in the savanna zone at higher numbers at a cattle ranch in Nyanga province. Leukoconcentration and Field's stain for L. loa diagnosis performed well as diagnostic tools. However, studies on diagnostic efficacy remain scant, and no study has focused on the evolution of L. loa at the wildlife-human interface of Gabon.

Role of Hematological Parameters in the Early Diagnosis of Neonatal Sepsis.

The major cause of neonatal mortality and morbidity is bacterial sepsis. Blood culture is the most reliable method in neonatal sepsis. This study was conducted to study the usefulness of hematological parameters in the early diagnosis of neonatal sepsis and to assess the most sensitive and specific variables in diagnosing neonatal sepsis. This prospective study was conducted in a tertiary care hospital from January 2017 to January 2018. Peripheral blood smears were prepared from patients with clinical suspicion of sepsis or predisposing perinatal factors for sepsis and stained with Field's stain and examined. The hematological findings were analyzed according to the hematologic scoring system of Rodwell. It was found that immature PMN count, I: M ratio, and I: T ratio had the highest sensitivity (92.06%, 87.30%, and 74.60%, respectively) while I: M ratio, I: T ratio, and degenerative changes in PMN had the highest specificity (97.50%, 96.50%, and 94.0%, respectively) in the prediction of sepsis.

Performance of Field's Stain Compared with Conventional Giemsa Stain for the Rapid Detection of Blood Microfilariae in Gabon.

ABSTRACT.Filarial infections caused by Loa loa and Mansonella perstans are a considerable public health burden in rural regions of Central Africa. Rapid diagnostic tools for the detection of microfilariae in the blood are needed. Field’s stain is a rapid staining technique for microscopic slides originally established for malaria diagnostics. It requires less than 1 minute of staining compared with conventional staining protocols requiring at least 15 to 20 minutes for staining and could thus significantly accelerate diagnostics for human filariasis. Here we evaluated Field’s stain as a rapid staining technique in comparison to Giemsa stain for the detection of microfilariae in peripheral blood. Blood smears were collected from 175 participants residing in the region of Lambaréné and Fougamou, Gabon. Each participant’s samples were stained in parallel with Field’s stain and conventional Giemsa stain. Slides were then microscopically assessed and compared for qualitative and quantitative results by a blinded assessor for the two endemic filarial blood pathogens M. perstans and L. loa. Field’s stain shows excellent diagnostic performance characteristics for L. loa microfilariae compared with Giemsa staining. Concordance was favorable for M. perstans although lower than for L. loa. Field’s stain offers a rapid alternative to Giemsa stain for detection of L. loa microfilariae in thick blood smears. This could help accelerate diagnostics of blood filarial pathogens in mass screening programs or resource constrained health care institutions with high patient load.

Capacity of the clinical laboratories of the private sector at khartoum state-Sudan, for the parasite-based malaria diagnosis

Background: The parasite-based diagnosis (malaria microscopy) remains the gold standard method for diagnosis of malaria in endemic areas, where 600 million individuals are infected. Malaria is the most common cause of hospital visits in Sudan. Objective: This study is aimed to assess and evaluate the capacity and quality of the Clinical Laboratories of the private sector at Khartoum State-Sudan, for the parasite-based malaria diagnosis. Method: 70 clinical laboratories form the private sector, were enrolled in this study.The quality and capacity for the study subjects were assessed and evaluated using novel scoring system. Six quality identifiers were selected as key performance indicators. The quality identifiers and their score were as follows: personnel (20%), microscope (25%), staining (20%), blood film and slide (15%), result and report (10%), and Building and safety (10%). For the evaluation of the quality and capacity of study subjects, the cutoff point was identified as (≥ 60%). Results: 64 (91.4%) individuals in this study have a bachelor degree in Medical laboratory sciences; only three of them major in Parasitology. 60 (85.7%) of the personnel have more than three years of experience in malaria diagnosis. Only 10% of the personnel in this study attended in-service training in malaria diagnosis. 58 individuals (83%) scored 10 or more for the total personnel quality score. For the quality of microscope, all the study subjects scored at least 15 points. Almost all the study subjects used Giemsa's stain, with only 5.7% using Field's stain. For the staining quality score, 52 subjects (74.2%) scored more than 10 points. Only 35.7% of study subjects reported the species of Plasmodium. 77.1% of study personnel reported the stage. Conclusion: Of the subjects, 88.5% were of a good quality and they were of an acceptable capacity for parasite-based malaria diagnosis. The quality could be improved by implementing an incentive program for quality inspection.

A study of the relationship between the observation of fever symptoms and parasitemia among children in the Federal Capital Territory, Nigeria

Background: Fever is usually associated with malaria parasitemia, and it is recommended that febrile children below the age of 5 years be treated with antimalarials. This study was undertaken to obtain information concerning the relationship between fever and the prevalence of malaria parasitemia among Nigerian children. Materials and Methods: Blood specimens from deep finger pricks of 730 children aged 0-2 years were examined for parasitemia using the Field's stain method, and the axillary temperature of each subject was measured. Results: Malaria parasites were observed in 26.1% of the afebrile children and 40.6%, a statistically significant difference, in febrile children. Furthermore, 59.2% of the febrile subjects had no detectable malaria parasites in their blood. Conclusions: Fever is not always indicative of parasitemia, and subjects with asymptomatic infection must be regarded as a significant reservoir of transmissible malaria parasites within the study environment.

Peripheral Blood Film Examination In Malawi: The Maximum Diagnostic Information for the Least Resources?.

AbstractAbstract 3799 Introduction:Malawi is the 23th least developed country according to the 2009 UN human development index and has a per capita health expenditure of $17 per year. In common with most of sub-Saharan Africa, severe haematological abnormalities are common in hospital patients, both contributing to ill health and reflecting the nature of underlying illnesses. Facilities for investigating abnormal results are limited and there are chronic problems with supply and maintenance of equipment and reagents. Examination of peripheral blood films provides extensive diagnostic information and can be performed with equipment routinely available even in district laboratories but there are few data on the feasibility and utility of routine blood film examination in this setting. Methods:Routine preparation of thin blood films stained with reverse Field's stain was introduced as a laboratory standard operating procedure for all FBC results meeting predetermined criteria [Hb<7.0 or >16.5 g/dl; MCV<60 or>100 fl; WBC <3.5 or >17.0 ×109/L; PLT <70 or >650 ×109/L] in the major teaching hospital. Films were reported by an experienced haematologist. Handwritten laboratory records of FBC and blood film reports over a 12 month period were reviewed retrospectively. Results:From 35449 FBC samples received 9543(26.9%) met criteria for film preparation. 3745 (39.2% of samples meeting criteria) were prepared. The proportion of films made improved during the study period; films were less likely to be prepared at weekends or late in the day. High day-to-day variability suggests that compliance levels may reflect staff on duty on individual days; workload on a given day did not appear negatively correlated with compliance. 69.5% of film reports gave added diagnostic information (other than simply confirming automated counts); many of the features found were not evident from the patient's clinical condition. Important findings included 33 new cases of leukaemia (14 acute leukemia, 6 CML and 13 CLL or other lymphoid disorders). 6.5% of films showed features suggesting haemolysis or increased red cell production. 2.2% showed specific features (not just macrocytosis) suggesting megaloblastic anaemia, 4.7% showed malaria parasites or other evidence of malaria such as pigment. 2.5% of films showed features raising the possibility of error in the automated counts. Reactive features were very common (57% of films). The 10 most common classes of film findings [see table 1] accounted for 75.8% of informative blood film reports.Table 1:Ten most frequent blood film findings in MalawiReportFrequency (% of informative films)“Reactive neutrophils”28.8Rouleaux20.6Neutrophil left shift16.0Iron deficiency features12.6P.Falciparum5.0Macrocytosis4.0Neutrophils appear normal3.6Polychromasia3.3Target cells2.0Oval macrocytes1.3 Conclusions:Routine peripheral blood film examination in a sub-Saharan African context provides a high yield of diagnostic information with minimal extra equipment requirement. A small number of common findings account for the majority of reports, suggesting that focussed training to identify these common abnormalities could have substantial benefits and could be implemented in a brief training programme. The variable compliance with the standard operating procedure suggests that staff confidence and enthusiasm may be the most important barriers to the incorporation of film reporting into routine practice. Disclosures:No relevant conflicts of interest to declare.

The performance of health laboratories and the quality of malaria diagnosis in six districts of Tanzania

Early laboratory diagnosis is critical for the optimal management of human malaria, particularly following the introduction of relatively expensive, artemisinin-combination therapies (ACT). The performance of the laboratories and the quality of malaria diagnosis have recently been assessed in 36 healthcare facilities in six districts of Tanzania. Questionnaires, checklists and observations were used to collect information on the availability and functional status of equipment as well as on laboratory personnel and their performance in malaria diagnosis. Together, the surveyed facilities had 112 laboratory staff [almost half (41.1%) of whom were laboratory assistants] and 57 microscopes. Twenty-seven (75.0%) of the healthcare facilities included in the survey had only one functional microscope each. Only seven (12.3%) of the assessed microscopes had been serviced in the previous 2 years. Of the 38 microscopists who were assessed, 24 (63.2%) were re-using microscope slides, 29 (73.5%) were producing bloodsmears of low quality, and 30 (79.0%) were using Field's stain. Although the facility microscopists gave similar results to experienced research microscopists when reading bloodsmears prepared by the survey team, using high-quality reagents (kappa=0.769), they appeared far less competent when reading smears stained using the reagents from the study laboratories (kappa=0.265-0.489). The quality of malaria diagnosis at healthcare facilities in Tanzania, which is generally poor (largely because of inadequate supplies of consumables and the limited skills of laboratory staff in the preparation of bloodsmears), urgently needs to be improved if the utilization of ACT is to be sustainable.

Challenges in the diagnosis and management of sleeping sickness in Tanzania: a case report

In Tanzania sleeping sickness presents a serious threat to human health with a country-wide average of 400 cases reported annually. Both wild and domestic animals have been found to play a significant role in the epidemiology of sleeping sickness. Serengeti National Park in northern Tanzania, has experienced a number of sleeping sickness epidemics since 1922. The epidemics were associated with abundant game animals in the areas and Glossina swynnertoni was incriminated as the main vector. However since 2001 there has been no case of sleeping sickness reported from the park. This case report highlights on the possibility of resurgence and challenges in the diagnosis and management of sleeping sickness in Serengeti. A 38 years old Tanzanian man working in the Serengeti National Park who had experienced various tsetse bites was presented with a febrile condition and history of unsuccessful case management at different health facilities. Blood and cerebrospinal fluid (CSF) samples were examined for the presence oftrypanosomes using wet film, Field's stain and concentration techniques. Typanosoma brucei rhodesiense were detected in both the blood and CSF samples. The patient was treated successfully with melarsoprol. The results of this case study highlight the possibility of resurgence of sleeping sickness in the park hence calls for the need to create more awareness among the community and clinicians. There is need for early reporting to health facility and strengthening the diagnostic capacity of healthcare facilities in and around national parks endemic for sleeping sickness.

Validez del diagnóstico presuntivo de leishmaniasis cutánea realizado por mediadores comunitarios en Colombia

To validate a method for the presumptive diagnosis of cutaneous leishmaniasis based on the observation of clinical-epidemiological criteria, carried out by community health workers in three endemic municipalities in Santander, a department in northeastern Colombia. This evaluation study of diagnostic technologies was based on a cross-sectional sampling of suspected cases of cutaneous leishmaniasis in the municipalities of Rionegro, El Playón, and Landázuri. After being trained, the community health workers carried out the presumptive diagnoses of cutaneous leishmaniasis between October 2004 and November 2005. At the time of diagnosis, the health workers also collected samples for confirmatory diagnosis through Field's stain method, culturing, and polymerase chain reaction. Four criteria were used to assess the validity of the presumptive diagnoses carried out by the health workers: sensitivity, specificity, positive predictive value, and negative predictive value. Replicability among the health workers was estimated through their observed level of agreement. According to the laboratory tests, of the 196 patients studied, 33 (16.8%) were negative and 163 (83.2%) were positive. For all the levels of certainty of the clinical diagnosis, the sensitivity was between 52% and 98% (kappa(1, 0) = 39.0%) and the specificity between 9% and 55% (kappa(0, 0) = 14.0%). The area under the receiver operating characteristic curve was 56.5% (95% confidence interval: 45.6% to 67.4%). The proportion of positive agreement and of negative agreement was 86.3% and 43.5%, respectively. The sensitivity of the presumptive diagnosis carried out by the health workers surpasses that of the parasitological diagnostic methods generally used in the three endemic areas, but its specificity is much lower. Even though this approach is not useful as a diagnostic test for cutaneous leishmaniasis or as a criterion for deciding to proceed with treatment or not, the method is useful for the active identification of cases in the community.

Evaluation of different methods for diagnosis of P. falciparum malaria

Rapid diagnosis is a prerequisite for institution of effective treatment and reducing the mortality and morbidity of falciparum malaria. This study was taken up to compare the efficacy of various rapid methods viz, acridine orange, Plasmodium falciparum histidine rich protein II antigen detection and Field's stain with traditional microscopy i.e, Leishman stain for diagnosing falciparum malaria. Thick and thin blood films of 443 consecutive patients with history of fever with chills and rigors were examined by Leishman and Field's method. Acridine orange stained wet mounts of blood were examined under fluorescence microscopy. All films were examined by two independent microbiologists. Plasmodium falciparum histidine rich protein II antigen was detected using commercially available kit, Paracheck Pf. Out of the 443 subjects examined for P.falciparum 18.28% were detected by Leishman stain, 6.32% by Field's stain, 18.28% by acridine orange and 18.1% by antigen based technique. Field's stain missed 53 (65.4%), while Paracheck Pf was negative in 6(7.4%) of the Leishman positive samples. All Field's stain and acridine orange positives were positive by Leishman, but five Paracheck Pf positives were negative. Leishman stain is cost effective but if facilities are available one should use acridine orange for screening. The antigen detection kits are rapid, simple and are useful but to rule out false negatives in clinically suspected cases, Leishman stain is reliable.

Field's stain a quick alternative to MGG (May Grunwald Giemsa)

Field's stain a quick alternative to MGG (May Grunwald Giemsa)

Immunoglobulin G and subclass responses to Plasmodium falciparum antigens: a study in highly exposed Cameroonians.

We conducted a cross-sectional study in Bolifamba village in the South West Province of Cameroon to determine antibody responses to crude Plasmodium falciparum antigens. A total of 347 subjects were examined. Parasite counts were obtained on thick blood films stained with Field's stain. Total immunoglobulin (Ig)G and IgG subclass levels were determined in serum samples from four groups comprising children 1 to 5 years old and adults > or = 18 years with or without falciparum malaria parasites, using enzyme-linked immunosorbent assay with crude blood-stage antigens of Plasmodium falciparum strain F32 as target. Depending on the age group, malaria prevalence varied between 10% and 65% with a mean of 30.8%. Prevalence rate and parasite density declined with increasing age. Total IgG and IgG1-3 levels were significantly higher in adults than in children (p < 0.05). Parasite-bearing individuals in both age groups had higher IgG titres than their non-infected counterparts, while subtype levels were not significantly different (p = 0.05). These findings indicate that Bolifamba village could be a convenient site to study further the protective immunity to malaria.

Field's stain--a rapid staining method for Acanthamoeba spp.

Acanthamoeba sp. is a free-living amoeba known to cause chronic central nervous system infection or eye infection in humans. Many cases remain undetected for want of a good detection system. We report for the first time a rapid staining method to facilitate the identification of Acanthamoeba sp. using the modified Field's staining technique. A. castellanii, which was used in the present experiment, is maintained in our laboratory in mycological peptone medium (Gibco). The cultures were pooled together and smears were made on glass slides for staining purposes. Different types of stains such as Field's stain, modified Field's stain, Wright's stain, Giemsa stain, Ziehl-Neelsen stain, and trichrome stain were used to determine the best stain for the identification of this amoeba. The concentration of various stains and the duration of staining were varied to provide the best color and contrast for each stain. Acanthamoeba was also obtained from the brain of experimentally infected mice and was stained with various stains as mentioned above to determine the best stain for use in identifying the presence of this parasite in experimentally infected animals. The modified Field's stain gives a very good color contrast as compared with other stains. Furthermore, it takes only 20 s to be carried out using the least number of reagents, making it suitable for both laboratory and field use.

The laboratory diagnosis of malaria

Summary Audits of malaria diagnosis in the UK have revealed shortcomings. The use of recommended procedures should improve the standard of malaria diagnosis. Both thick and thin films should be examined. Thick films should be stained unfixed with a Giemsa or modified Field's stain. Thin films should be fixed and stained with a Giemsa or a Leishman stain. All films should be examined for an adequate period of time by two observers. In the case of P. falciparum infection parasites should be quantified. Microscopy may be supplemented by an immunological or fluorescence-based method. Slides from all cases in which a diagnosis of malaria is made should be sent to a reference centre for verification. Laboratories should participate in a relevant NEQAS scheme and should take steps to ensure that all those carrying out malaria diagnosis maintain their skills.

Versatile Field's stain.

Versatile Field's stain.

Tetrapetalonema dunni sp. n. (Nematoda: Filarioidea) from Malaysian Tree Shrews

Tetrapetalonema dunni, a new species of filariid from Malaysian tree shrews, is described, based on specimens obtained from Tupaia glis. The parasite has been found in several Tupaia species from the Malay Peninsula and North Borneo. T. dunni is much smaller in both adult and microfilarial stages than T. marmosetae or T. tamarinae, to which it seems most closely related, and it is the only one of these 3 species found in Asian primates. Dunn (1964) reported, without describing it in detail, an unsheathed microfilaria in samples of blood taken from tree shrews (Tupaia spp.) collected on the Malay Peninsula and in North Borneo. Subsequently, each of us, while independently engaged in studying parasites of tree shrews at the Institute for Medical Research in Kuala Lumpur, Malaysia, and at the Delta Regional Primate Research Center of Tulane University in Covington, Louisiana (USA), collected the same microfilaria, together with adult worms. This report describes adult worms recovered at necropsy from the subcutaneous tissues of Tupaia glis and T. tana in Malaysia and records observations on the apparent host and geographical range of the parasite, based on data collected from 1965 to 1971. MATERIALS AND METHODS The presence of microfilariae in animals was detected by examining heart blood laked and sedimented in 2% formalin (Knott, 1939), then stained with methylene blue (1:1,000) or by examining thick blood films also prepared from heart blood and stained with Field's stain. For Received for publication 13 June 1972. * This work was supported in part by the University of California International Center for Medical Research and Training (UC ICMRT) through research grant AI 10051 to the Department of International Health, School of Medicine, University of California, San Francisco, and research grant No. FR 00164 DRFR, both from the NIH, U. S. Public Health Service. t Institute for Medical Research, Kuala Lumpur, Malaysia, and the Department of International Health, University of California, San Francisco, California. + Tulane University, Delta Regional Primate Research Center, Covington, Louisiana 70433. Requests for reprints should be sent to the Editor, G. W. Hooper Foundation, University of California, San Francisco, California 94122, USA. detailed study of the microfilaria, additional thick blood films were stained with dilute Giemsa (35 drops/100 ml buffer, pH 7.2) for 45 to 60 min. At necropsy, adult worms were either teased from the tissues with fine dissecting needles or were recovered by soaking the skin and carcass in warm, physiological saline solution. Worms were fixed in glacial acetic acid for a few minutes (Berland, 1961), transferred to 70% ethanol containing 5% glycerin, then cleared in pure glycerin fo study. En face mounts were prepared according to the method of Anderson (1958). A modification of the same technique was employed in visualizing the spicules and caudal papillae. Study of the spicule morphology was aided by the partial digestion of the male tail in a 10% solution of Cl rox (sodium hypochlorite). All measurements are in microns unless otherwise noted; ranges are followed by the means in parentheses. Drawings were made with the aid of a camera lucida or similar device.

The preparation and stability of Field's stain.

The preparation and stability of Field's stain.

Malaria among prisoners of war in Siam (“F” Force)

1. 1. The 7,000 British and Australian prisoners of war who formed “F” force, left Changi camp on Singapore Island in April, 1943, and 3,122 returned in December, 1943. They had spent the intervening 8 months in the hilly jungle country of Siam, about 200 miles north-west of Bangkok near the Three Pagodas pass on the Siam-Burma border, constructing a section of a new railway to link Bangkok and Moulmein. 2. 2. Few had had malaria before leaving Changi. Those who returned had a malaria parasite rate of 25·7 per cent. (801/3,122), and a malaria attack rate during 7 weeks of January to February, 1944, of 18·8 per thousand men per day. 3. 3. Field's rapid stain proved of great value. Its independence of alcohol and the pH of the water available, and its extreme economy in use, made it ideal for our purpose. 4. 4. Plasmodium vivax was at all times the commonest species of parasite; in the later months it completely outnumbered P. falciparum, and the picture presented was that of chronic relapsing vivax malaria in a debilitated population. 5. 5. Quinine, when available in sufficient quantity, effectively cured attacks of malaria, but recurrences in a few weeks were commonplace. 6. 6. Malaria was recorded as a cause in 11 per cent. of all deaths (338/3,087), but there is reason to think that it was contributory to many more. 7. 7. Anopheles maculatus and A. minimus were considered to be the principal vectors, though A. leucosphyrus may also have played some part in transmission; these judgements, however, are based on larval surveys only, and lack the definite proof afforded by trapping and dissection of adult mosquitoes. 8. 8. Larvae of Anopheles aitkeni and A. barbumbrosus were found. These species do not appear to have been reported from Siam before. 9. 9. We confirm Anigstein's opinion of the malarious nature of hilly regions in Siam, but differ from him by suggesting that the season of greatest transmission in this particular region is more likely to be the wet season than the dry. He thought that agriculture in the hilly regions, which involved irrigation, usually made the malaria worse. This is in line with our findings that the two camps situated near abandoned rice fields were the most malarious.