A Cluster of Cryptic Plasmodium falciparum Malaria in African Migrants in Southern Italy,October 2017

Abstract

Background:

Italy was declared malaria free by the World Health Organization in 1970. Despite this, nonimport malaria cases are on the increase in Italy and throughout the Mediterranean area. In Italy, in the period between 2011 and 2015, seven cases of locally acquired malaria have been reported, including one introduced case of Plasmodium vivax; moreover, the last certain case of introduced malaria (by P. vivax) has been reported in Tuscany in 1997. No case of introduced malaria from Plasmodium falciparum has been reported in Italy since 1970.

Case Presentation:

A cluster of four cryptic P. falciparum malaria cases were ascertained in migrant farm workers (three from Morocco and one from Sudan) in Apulia (southern Italy) with clinical onset between September 20 and 27, 2017. None of the patients reported a history of a recent trip to malaria-endemic areas or hospitalization or other risk factors. Typing of malaria was also confirmed using molecular biology methods in two different laboratories. There were no cases of severe malaria in our four patients, and only one in need of transfusion. All patients were discharged cured after being treated with mefloquine due to the unavailability of other antimalarials.

Conclusions:

In recent years, numerous reports of locally acquired malaria have been made in southern Europe. The cases described in this article represent the first cluster of malaria caused by P. falciparum in Europe. Today, clinical presentation in the diagnosis of malaria is more important than ever, since epidemiological criterion cannot be considered unfailing. The mode of transmission has not been proven and further biological and entomological studies are necessary to define our case as cryptic or confirm the presence of mosquitoes capable of transmitting P. falciparum and/or the capacity of Anopheles labranchiae, An. superpictus, or An. plumbeus to transmit it on Italian territory.

Background

Malaria (also called paludism) is a parasitosis caused by protozoa parasites of the genus Plasmodium. Among the various species of the Plasmodium parasite, four are the most widespread, whereas the most dangerous is the Plasmodium falciparum, with the highest mortality rate among infested subjects. The parasite reservoir is represented by chronically infected individuals. The vectors are mosquitoes of the genus Anopheles (An) (WHO 2018).

Italy was declared malaria free by the World Health Organization (WHO) in 1970, after an intense vector control program implemented during the period 1947–1951 (Majori 2012). However, in many Italian regions, particularly in the south, mosquitoes capable of transmitting plasmodium such as An. labranchiae and An. superpictus are present. Therefore, indigenous transmission due to a suitcase event or to the presence of a local vector capable of transmitting malaria or a vector-adapted pathogen cannot be excluded (Italian Ministry of Health 2016).

The first half of the 20th century saw a continuous reduction of cases of malaria in Europe, thanks to a combination of improved economic conditions and the regular implementation of control measures. In Italy, the reduction of malaria endemicity registered during the same period was mainly due to the approval of laws of great social importance (Majori 2012). Today many of the world's climatically temperate areas (e.g., the Mediterranean basin and southern regions of the United States) are once again at risk of a new introduction of malaria, due above all to the dynamics of migration the increasing number of intercontinental flights (European Centre for Disease Prevention and Control 2017, Mace et al. 2018). Between 2011 and 2015, a total of 3633 cases of malaria were reported in Italy, 7 of which were locally acquired (two induced, three cryptic, one imported with baggage, and one introduced) (Italian Ministry of Health 2016). The only certain case of introduced malaria in Italy was a case due to Plasmodium vivax and occurred in Tuscany in 1997 (Baldari et al. 1998); moreover, two more P. vivax cases defined as “probable autochthonous introduced” were notified from two sites in south-central Italy in 2009 and 2011 (Romi et al. 2012a).

In 2016, there were only 10 cases of locally acquired malaria (introduced and airport malaria) in Europe, occurring in Greece, France, Spain, and Lithuania with no sustained transmission at local level (European Centre for Disease Prevention and Control 2017). In 2017, in Greece six cases of locally acquired malaria were recorded (Hellenic Center for Disease Control and Prevention 2017). Five of these cases were caused by P. vivax and classified as locally acquired introduced malaria, one was caused by P. falciparum. The mode of transmission of the latter case was not clearly defined (mosquito vector or nosocomial transmission) (Hellenic Center for Disease Control and Prevention 2017). No case of P. falciparum introduced malaria has so far been described in Europe. In this article, we report four cases of autochthonous P. falciparum malaria in migrant farm workers in the southern Italian region of Apulia in October 2017. The exact mode of transmission has not been yet defined.

Case Report

In this study, we report a cluster of four cases of P. falciparum. malaria occurring in a rural area of Taranto province (southern Italy) between September 26 and October 2, 2017 in seasonal farm workers. Cases were reported to the Regional Epidemiologic Observatory by the Local Health Unit of Taranto. All four patients were male immigrants (three Moroccan, all from the town of Settat, and one Sudanese) without a permit to stay in Italy. They had an average age of 29 years, and lived in Contrada Pantano, a rural area in the municipality of Ginosa (Taranto Province), far from the regional airports. The patients lived in dwellings close to the fields and to the Bradano River, but did not live in the same house. None declared having been in areas where malaria is endemic in the previous 36 months, nor having other epidemiological risk factors for malaria indicated by the Ministry of Health (Italian Ministry of Health 2016), which would have made it possible to deny the possibility of an autochthonous case (Table 1). In particular, none of the four patients had travelled in areas where malaria is endemic in the previous 36 months, undergone blood transfusion or tissue/organ transplantation or hospitalization; taken drugs intravenously, received baggage/parcels/visitors from malaria endemic areas, lived near to international airports (<5 km) or storage areas or stores of imported products from tropical areas (<500 meters).

Table 1.

Biohumoral Parameters

Parameters	Pt. 1		Pt. 2		Pt. 3		Pt. 4
Parameters	Ad	Dis	Ad	Dis	Ad	Dis	Ad	Dis
White blood cells ( × 10^3/mL) (norm: 4.00–10.00)	6270	6390	8130	10700	8010	25530	7590	7920
Hemoglobin (g/dL) (norm: 14–18)	14.4	11.5	13	11.9	13.5	10.4	7.9	9.4
Hematocrit (%) (norm: 42.0–52.0)	41.7	34.1	39.3	36.7	38.9	30.9	23.4	27.5
Platelet count ( × 10^3/mL) (norm: 140–440)	146	382	47	228	25	47	15	198
Prothrombin time (%)(norm: 70–120)	68.4	ND	72.6	ND	69.7	ND	ND	ND
INR (norm: 0.8–1.2)	1.18	ND	1.14	1.07	1.16	ND	1.23	ND
Fibrinogen (mg/dL) (norm: 200–400)	292	ND	447	ND	447	ND	ND	ND
Glucose (mg/dL) (norm: 65–110)	98	74	123	81	107	98	108	89
Creatinine (mg/dL) (norm: 0.44–0.9)	0.72	0.75	0.95	0.63	1.42	0.69	1.40	0.70
Alanine aminotransferase (U/L) (norm: 12–65)	22	123	43	115	49	51	22	59
Sodium (mEq/L) (norm: 135–145)	136	138	134	138	123	139	130	137
Total bilirubin (mg/dL) (norm: 0.2–1)	0.70	0.30	3.00	0.90	4.20	0.80	2.20	1.10
LDH (U/L) (norm: 84–246)	425	388	776	287	848	283	623	430
C-reactive protein (mg/dL) (norm: <0.08)	1.5	ND	8.7	ND	12.1	ND	ND	ND
Procalcitonin (ng/mL) (norm: <0.5)	28.31	ND	16.64	0.45	44.16	2.89	36.2	4.49
HIV 1–2 Ag/Ag (norm: neg) ND	Neg	ND	Neg	ND	Neg	ND	Neg	ND
Urine screening test for drugs^a (norm: neg)	Neg	ND	Neg	ND	Neg	ND	Neg	ND
Longitudinal splenic diameter (mm)	129	ND	135	124	170	166	135	121

Including amfetamine, benzodiazepine, cocaine, ecstasy, marijuana, methadone, and opiates.

Ad, hospital admission; Ag, antigen; Dis, hospital discharge; HIV, human immunodeficiency virus; INR, international normalized ratio; LDH, lactate dehydrogenase; ND, not done; Neg, negative.

All had fever, abdominal pain, vomiting, and diarrhea; one also presented intense asthenia and another complained of a headache. All patients had severe thrombocytopenia with increased levels of procalcitonin and lactate dehydrogenase. One patient required a blood transfusion. In Table 1, the main biohumoral parameters of the patients at admission and at discharge are reported.

The diagnosis of malaria, particularly in the first patient, was made particularly difficult due to the absence of the epidemiological criterion of having travelled to a country where the disease is endemic. It was made possible by the persistence of the fever that led the patient to go to accident and emergency department of a local hospital on two occasions and due to the presence of thrombocytopenia and high levels of serum procalcitonin in the absence of other clinical and laboratory signs, which suggest bacterial sepsis (absence of neutrophilic leukocytosis, C-reactive protein values that are not particularly high). The diagnosing patients 2–4 was obviously easier and determined by the epidemiological link existing between the four patients).

The microscopic examination of peripheral blood smears was performed for malaria diagnosis. The patients' blood and urine samples underwent molecular detection of P. falciparum at the Laboratories of Clinical Pathology of Taranto's Hospital and of Molecular Epidemiology and Public Health of Bari's Polyclinic Hospital. Total nucleic acid was extracted using the MagnaPure LC automated extraction system (Roche Diagnostics, Milan, Italy). A commercial multiplex real-time PCR kit (FTD, Tropical Fever Core, FastTrack Diagnostics, Luxembourg) was then used for the detection of Plasmodium spp. and subsequently for the differentiation that resulted in P. falciparum species (FTD, Malaria Differentiation, FastTrack Diagnostics, Luxembourg).

Epidemiological investigations and clinical presentation

Case 1

The first Moroccan patient, 21-year-old, came from Libya and landed in Sicily in June 2017, before spending 2 months in Salerno (Campania) and then moving on to Contrada Pantano in Ginosa where he had lived since August 2017. The patient reported that he lived in a house with case 4 and 3, other countrymen without reported risk factors. The patient went to the emergency room at Castellaneta Hospital (near Taranto city) on September 22 with fever and vomiting on the same day and was recommended to receive clarithromycin therapy. Because of the persistence of vomiting and fever and the difficulty in taking therapy, the patient returned to the same emergency room from where he was admitted on September 25. On September 28, emoscopic test was performed due to the persistence of symptoms.

Case 2

The 37-year-old Sudanese patient reported having been in Italy since 2008 and had been living in Contrada Pantano since August 2016 along with other Sudanese; none of whom, however, had undertaken international travel in the previous 3 months or had received any kind of expedition from areas considered as endemic for malaria. The patient was admitted to Internal Medicine Department of Castellaneta Hospital on September 20, 2017 and, after 10 days, on September 30, because of fever persistence, was transferred to our department of infectious disease where emoscopic test was performed. He lived at home with nine other immigrants (five from Mali and four from Sudan) who did not report travel or reception of baggage from endemic areas or other risk factors.

Case 3

A 23-year-old Moroccan patient who reported to have arrived in Italy in 2008 and to have lived in Salerno until the beginning of 2017. He then left for Morocco, but returned to Italy (Potenza, Basilicata) in July 2017 and moved to Contrada Pantano at the beginning of September of the same year. As in the first case, also case no. 3 went twice to the Castellaneta Hospital's emergency room on September 28 and October 1 when he was admitted to our ward because of the persistence of fever.

Case 4

The last case is a 35-year-old Moroccan man who reported to have landed in Sicily in 2006. He then reached Salerno and lived there for a few years before moving to Contrada Pantano in 2010 where he lived with four other Moroccans (one of whom was patient case no. 2). He was admitted to hospital on October 2 after access to the emergency room of the Hospital of Castellaneta on September 28 due to abdominal pain, diarrhea, and vomiting.

Discussion

The epidemiological investigation conducted may present inaccuracies in consideration of the information obtained from highly mobile migrant subjects on the country as already described in a case of cryptic malaria recently discovered in Tuscany in a Moroccan patient (Zammarchi et al. 2018).

Owing to the rise in intercontinental travel and, to a lesser extent, an increase in migratory flows, the number of malaria cases diagnosed in Italy and throughout the Mediterranean basin is continuously increasing: about 800 cases/year in the past 2 years have been notified (Italian Ministry of Health 2016). The most recent epidemiological data (2011–2015), count 3633 cases notified in Italy, almost all of which were imported (Italian Ministry of Health 2016). Only seven are the indigenous cases reported in this study, two were induced (P. falciparum and P. malariae), three cryptic (one of P. falciparum and two of P. malariae), one introduced with baggage (P. falciparum), and just one introduced (P. vivax), that is, transmitted by indigenous vectors (Italian Ministry of Health 2016). WHO defined “induced” case of Malaria when the disease is caused by an agent introduced parenterally (transfusions, transplants) and “cryptic” case of Malaria if, after careful epidemiological investigation, it is not classifiable in any of the categories described (WHO 2018).

Public health measures have been targeted to set up specific integrated epidemiological, entomological, and environmental surveillance. Whereas emoscopic screening on all migrants from endemic area appears difficult as it is time consuming, not very effective in patients with low parasitemia, and not possible to carry out in irregular migrants and tourists, and so on, rapid diagnostic tests recommended by the WHO help to reduce the number of undiagnosed cases. However, limiting this screening to symptomatic patients (with fever) would not solve the problem; in fact, by definition the carrier is generally asymptomatic (WHO 2020).

In Italy, there are at least three species of mosquito capable of transmitting malaria: An. labranchiae that belongs to An. maculopennis complex that in recent decades has been found in most of the country (central-southern regions and islands); An. superpictus that is instead present in small circumscribed areas near waterways in southern Italy (especially Calabria) (Italian Ministry of Health 2016); and finally An. plumbeus always signaled in Sicily and Sardinia has been reported recently in the Trento province (Tagliapietra et al. 2019). The most recent official document published by the Ministry of Health also reported that while “the sensitivity of An. labranchiae and infection with P. vivax strains, coming from endemic areas, has been ascertained from the occurrence of autochthonous cases, … it is less probable with P. falciparum afro tropical strains” not yet found in Italy (Italian Ministry of Health 2016).

Moreover, An. plumbeus is considered to be an efficient carrier of malaria (Eurasian strains of P. vivax and tropical strains of P. falciparum) (Bueno-Mari and Jimenez-Peydro 2012), but it is thought to be of minor importance in transmission due to its ecology (Becker et al. 2010). A recent study demonstrated laboratory infection of An. plumbeus females (from Switzerland) with a tropical strain of P. falciparum, showing an overall infectivity of 94% (45 out of 48 individuals) in one experiment (Schaffner et al. 2012), suggesting that this species could play a significant role in the local transmission of imported malaria. Experimental data have shown that British An. plumbeus are susceptible to infection with P. falciparum, at least to the oocyst stage (Marchant et al. 1998).

Regarding the migrants' countries of origin, Morocco has been classified as free from malaria since 2010, not having documented any autochthonous cases since 2007 (WHO 2017), whereas Sudan is considered to be an endemic area at high risk of P. falciparum all year round.

Based on the period of clinical onset, malaria's average time of incubation and place of habitation and work, the cases could be locally acquired, probably after exposure to a common source, although this has yet to be identified. The common source may have been a subject from an endemic area as asymptomatic carrier of the infection. However, no other cases of Malaria have been diagnosed in the Taranto area in 2017–2018.

Incubation times, however, do not support infection acquired in the country of origin and do not coincide with the incubation period of P. falciparum (normally between 9 and 30 days) (Harinasuta and Bunnang 1988).

The possibility that the Moroccan patient developed the disease in Morocco in July of the same year is most unlikely both because Morocco is defined as “malaria free” and because of the long incubation period. However, the possibility of prolonged incubation has recently been reported (Ashley and White 2014). Airport malaria transmission should be excluded, considering that the nearest airports (located in Gioia del Colle, Bari, and Brindisi city) are between 50 and 100 km from the rural area where patients lived, as should the possibility that transmission was caused by an infected mosquito carried in baggage. Other trips to endemic areas, or other risk factors for induced malaria such as blood transfusions, transplants, and intravenous drug use, have been excluded. The role of a local vector capable of transmitting malaria or a vector-adapted pathogen cannot be excluded.

In conclusion, there are no epidemiological risk factors indicated by the Ministry of Health to be excluded necessarily to confirm a suspected indigenous case. Malaria vectors are present in Italy and according to the latest available entomological data, An. labranchiae is present in Apulia (as well as in Calabria, Sicily, Sardinia) (Romi et al. 2012a). Studies conducted in Italy and in France on vectorial capacity of An. labranchiae showed that the species is capable but poorly susceptible to infection with tropical or African P. falciparum strains (de Zulueta et al. 1975, Toty et al. 2010, Romi et al. 2012b).

The epidemiological survey, however accurate, could be affected by the high housing rate and high number of migrants originating from endemic malaria countries, in the same area.

In conclusion, just as we must necessarily suspect malaria when a patient returns from an endemic area with fever and symptoms of the disease, we should not count out the same possibility when a patient does not have a history of travel in tropical areas.

Declarations

Ethics approval and consent to participate

The study did not require approval from the ethics committee, according to the Italian law, since it was performed in the context of normal clinical routines (art.1, leg. decree 211/2003). However, all patients referring to our institute provided consent for the use of their data for research purposes. In any case, data were previously anonymized, according to the requirements set by Italian Data protection Code (leg. Decree 196/2003).

Footnotes

Acknowledgment

We thank Dr. Ian Stanton for proofreading and translation checking.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

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