Download The African Eye Worm: A Case Report and

50
The African Eye Worm: A Case Report and Review
Sadia Ali, MD,* Melanie Fisher, MD, MSc,* and Gregory Juckett, MD, MPH†
*Section of Infectious Diseases and †Department of Family Medicine, West Virginia, Morgantown, WV, USA
DOI: 10.1111/j.1708-8305.2007.00166.x
Loiasis, caused by the filarial nematode Loa loa, is often asymptomatic but frequently manifests as episodic angioedema
and periocular migration of adult worms. Hence also known as the eye worm.1 It is rarely encountered in the United
States among travelers and immigrants. This report describes a case of loiasis in a Cameroonian student seen at a US
university clinic.
Case Report
A 30-year-old African student from Kumba, Cameroon, was evaluated in a university travel clinic for
a “foreign body sensation” in his right eye which
lasted for 5 hours. At the time of these symptoms, he
had visualized a thin, clear worm traveling across
the right eye. After the worm had passed, the foreign body sensation resolved but was followed with
intense conjunctivitis. His past history was significant for malaria 6 years ago but was otherwise unremarkable. He had been residing in the United States
for 2 years during which time he had no history of
international travel. He denied any migratory swellings or rash. On evaluation the following day, he
had conjunctival injection of the right eye, but no
worm was visualized on gross examination or on
evaluation under a slit lamp. Physical examination
was otherwise unremarkable.
Additional investigations showed a white blood
count of 6,400/␮L with 8% eosinophils (range:
1%–6%). Liver enzymes and renal functions were
normal. Peripheral blood smear drawn at 3 pm was
significant for the presence of sheathed microfilariae of Loa loa (Figure 1). The microfilariae were
quantified at 4,910 microfilariae/mL of blood.
Loa loa polymerase chain reaction was also positive,
establishing the diagnosis of loiasis. Concomitant
infection with onchocerca was ruled out by skin
Corresponding Author: Sadia Ali, MD, Robert C. Byrd
Health Sciences Center, Section of Infectious Diseases,
West Virginia University, PO Box 9163, Morgantown,
WV 26506-9163, USA. E-mail: [email protected]
snips taken from bilateral shoulders, hips, and
thighs. The patient was referred to the National Institute of Health for treatment and underwent
apheresis on hospital days 1 and 2. Subsequently, he
received prednisone 40 mg/d for 3 days which was
rapidly tapered. Diethylcarbamazine (DEC) was
then administered in incremental doses with 50 mg
on day 1, followed by 50 mg three times per day for
the next 3 days. The dose was gradually increased to
200 mg three times a day to complete 21 days of
therapy. Microfilarial quantification at the time of
discharge was 2,250 microfilariae/mL of blood.
The treatment was tolerated well. On follow-up
evaluation, no clinical relapse was detected and
blood smear was negative for any microfilariae. The
patient will be followed at 6-month intervals to
monitor for relapse.
Discussion
Loiasis is endemic in the rain forests of Central and
West Africa. Between 3 and 13 million people are
estimated to be infected with it.2 The presence of
three terminal nuclei and observation of sheathed
microfilariae (approximately 290 by 7.5 ␮m) in a
daytime blood specimen are features characteristic
of L loa. These characteristics help differentiate this
organism from the blood-borne microfilariae of
Wuchereria bancrofti and Mansonella perstans, whose
geographic distribution overlap that of L loa.3 The
microfilariae of M perstans are much smaller, have
no sheath, and have nuclei extending to the end of
the tail, whereas those of W bancrofti are sheathed
microfilariae seen only on specimens drawn at night.4
© 2008 International Society of Travel Medicine, 1195-1982
Journal of Travel Medicine, Volume 15, Issue 1, 2008, 50–52
51
African Eye Worm
Figure 1 Giemsa-stained peripheral smear from the
patient showing the presence of sheathed microfilaria of
Loa loa with nuclei extending to the tip of the tail.
Humans acquire L loa from the day-biting female
Chrysops fly, also known as the tabanid fly (horse fly
or deer fly). The fly infects humans with the thirdstage filariform larvae which mature into adult
worms over a period of 3 months to reside in the
subcutaneous tissue. Within a year, the adult worms
may produce thousands of immature larval microfilariae which can be detected in the blood stream. It
is the circulating microfilariae which are responsible for transmission of infections after being taken
up during the blood meal of female flies.3
Most people with L loa infection are asymptomatic. Disease manifestations are usually due to hypersensitivity reactions to the adult worms, and patients
often present with Calabar swellings due to transient
angioedema related to hypersensitivity reaction to
the adult parasite migrating through subcutaneous
tissue. The worm may also traverse the eye where it
may remain visible as a thin transparent worm for
hours before continuing its migration elsewhere.
Adult worms may survive for 4 to 17 years. Intense
itching, urticaria, and elevated eosinophil counts may
be seen during the course of the illness.2 The most serious complication of L loa infection is meningoencephalitis, which may result as a potential consequence
of high microfilarial load in the cerebrospinal fluid.
Following treatment, dying microfilaria generate a
host immune response when microfilaria levels exceed 2,500/mL, which can result in multiple cerebral
infarcts, encephalitis, or cerebral edema.3
The treatment of L loa infection remains problematic despite recent advances made in anthelmintic
chemotherapy. The current recommended drug of
choice is DEC at a dose of 8 to 10 mg/kg/day for 21
days in gradual incremental doses. However, it is contraindicated in patients with elevated microfilariae
levels because of its association with severe neurological side effects.5,6 Though DEC is thought to be
curative in most cases, multiple courses of therapy
may be needed and relapses may still occur. DEC
has activity against both microfilariae and adult
worms, and therefore, a sustained decrease in microfilarial intensity occurs following treatment.7,8
Mild side effects including fever, urticaria, and Calabar swellings which occur shortly after initiation of
therapy generally respond well to corticosteroids or
antihistamines. Albendazole has been shown to
temporarily reduce microfilaremia when used for 3
weeks at doses of 200 mg twice a day; however, relapses are likely to occur.5,9,10
Concomitant L loa infection in patients with
underlying Onchocerca volvulus infection is particularly problematic. Agents like ivermectin which
were widely distributed throughout West Africa
for the safe and effective control of onchocerciasis
have been associated with severe post-treatment
effects including death when administered to
patients with concomitant L loa and O volvulus
infection.5,11 Due to these adverse effects, the public health use of this drug in the forest habitat of the
L loa vector has been constrained. Occurrence of
serious reactions was related to the intensity of
pretreatment L loa microfilaremia. The relative risk
of developing marked or serious reactions was significantly higher when the L loa load exceeded
8,000 microfilariae/mL and are particularly notable in patients with L loa microfilaria greater than
20,000 to 50,000 microfilariae/mL.5,11 Since our
patient was from an area endemic for both L loa and
onchocerca, skin snip testing was done initially to
rule out onchocerca. Apheresis was then performed
to decrease the level of microfilaremia before
administering escalating doses of DEC to minimize
the possibility of side effects.
This case illustrates how increasing travel has
made it possible for such tropical diseases to be seen
in nonendemic countries, usually in immigrants or
travelers returning from west and central Africa.
Knowledge regarding this disease entity is imperative to aid early recognition and to offer appropriate
treatment by physicians worldwide. This patient
was successfully treated and continues to remain
symptom free to date.
Acknowledgments
The authors are grateful to Dr Patricia Canfield for
providing the photograph and to Dr Amy Klion
of the National Institutes of Health for all her help
and guidance with this case.
J Travel Med 2008; 15: 50–52
52
Declaration of Interests
The authors state that they have no conflicts of
interest.
References
1. Nutman TM, Miller KD, Mulligan M, Ottesen EA.
Loa loa infection in temporary residents of endemic
regions: Recognition of a hyper-responsive syndrome with characteristic clinical manifestations.
J Infect Dis 1986; 154:10–18.
2. Klion A, Nutman TB. Loiasis and mansonella infections. In: Guerrant R, Walker DH, Weller PF, eds.
Tropical infectious diseases: principles, pathogens
and practice. Vol 2. Philadelphia, PA: Churchill
Livingstone, 1999:861
3. Klion A. Loiasis. In: Strickland GT, ed. Hunter’s
tropical medicine and emerging infectious diseases.
8th Ed. Philadelphia, PA: W.B. Saunders Company,
2000:754–756.
4. Grove DI. Tissue nematodes including Trichinosis,
Dracunculiasis and Filariasis. In: Mandell GL,
Bennett JE, Dolin R, eds. Principles and practice
of infectious diseases. Vol 2. 6th Ed. Philadelphia,
PA: Churchill Livingstone, 2000:3267–3275.
J Travel Med 2008; 15: 50–52
Ali et al.
5. Tabi TE, Befidi-Mengue R, Nutman TB, et al.
Human loiasis in Cameroonian village: A double
blind, placebo controlled, crossover clinical trial of a
three day albendazole regimen. Am J Trop Med Hyg
2004; 71:211–215.
6. Carme B, Boulesteix J, Boutes H, Puruehnce MF.
Five cases of encephalitis during treatment of loiasis
with diethylcarbamazine. Am J Trop Med Hyg 1991;
44:684–690.
7. Ottsen EA. Efficacy of diethylcarbamazine in eradicating infection with lymphatic dwelling filariae in
humans. Rev Infect Dis 1985; 7:34.
8. Wahl G, Geroges AJ. Current knowledge on the epidemiology, diagnosis, immunology, and treatment
of loiasis. Trop Med Parasitol 1995; 46:287.
9. Klion AD, Horton J, Nutman TB. Albendazole therapy for loiasis refractory to diethylcarbamazine treatment. Clin Infect Dis 1999; 29:680–682.
10. Klion AD, Massougbodji A, Horton J, et al. Albendazole in human loiasis: Results of a double blind,
placebo controlled trial. J Infect Dis 1993; 168:
202–206.
11. Gardon J, Gardon-Wendel N, Demanga N, et al. Serious reactions after mass treatment of onchocerciasis with ivermectin in an area endemic for Loa loa
infection. Lancet 1997; 350:18–22.