Nitte University Journal of Health Science
HUMAN DIROFILARIASIS: AN UNCOMMON CASE OF SUB
CUTANEOUS INFECTION WITH DIROFILARIA REPENS WITH A BRIEF
REVIEW OF LITERATURE
Sanjeev H , Rajini M , Prasad S.R
Assistant Professor, Department of Microbiology, K.S. Hegde Medical Academy
Associate Professor, Department of Microbiology, Sri Devaraj Urs Medical College, Tamaka, Kolar
Professor & HOD, Department of Microbiology, Sri Devaraj Urs Medical College, Tamaka, Kolar
Assistant professor, Department of microbiology, K.S. Hegde Medical Academy, Deralakatte,
Mangalore - 575018. Mobile No. : 99722 12280 E-mail : [email protected]
Dirofilaria are a group of arthropod borne filarial nematodes that cause infection in wide range of domestic and wild animals. Dirofilaria repens
is a common zoonotic infection in countries like Sri Lanka. Human infection with Dirofilaria repens is not widely recognized in India. Most of the
documented cases of human dirofilariasis recorded in India presented with ocular infections, affecting the eyelid, periorbital region and
occasionally the sub conjunctivae. Here we report a rare case of sub cutaneous dirofilariasis, which presented as a swelling at an uncommon
Dirofilariasis, Dirofilaria repens, Dirofilaria tenuis
D. repens is a common zoonotic infection in countries like
Dirofilaria are a group of mosquito borne filarial
Sri Lanka. Human infection with D. repens is not widely
nematodes that cause infection in wide range of
recognized in India. However, there is probably a focus of
domestic and wild animals. The widely recognized
human infection with D. repens in Kerala, from where
parasites among them are Dirofilaria immitis (D.immitis),
the agent of cardiovascular Dirofilariasis, and Dirofilaria
repens causing sub cutaneous infection. D. repens is a
An 18 year old female patient, hailing from Allepey
mosquito borne filarial parasite of the sub cutaneous
district of Kerala, presented with swelling on the right
tissue of domestic and carnivores such as dogs, cats and
side of the neck of six months duration. The swelling
foxes. Dirofilaria species may be divided into two groups:
increased in size in the past one week and was associated
subgenus Dirofilaria represented by Dirofilaria immitis,
which is characterized by smooth cuticle and normally
found in the right heart and pulmonary vessels of dogs,
On examination a 4cm x 3cm swelling was noted in the
the natural host ; and subgenus Nochtiella, which
right supraclavicular region (Figure1). The surface of the
parasitize the sub cutaneous tissue. Species of this group
swelling was smooth and the borders ill defined. It was
have longitudinal ridges on the cuticle. Representative
not fixed to the underlying muscle or deeper tissue. The
species are Dirofilaria (Nochtiella) repens, found in dogs
swelling was tender on palpation and redness was noted
and cats, and Dirofilaria tenuis, found in raccoons .The
over the swelling. No similar swelling was noted
mature D. repens live in the tissues and organs of
e l s e w h e r e . C l i n i c a l d i a g n o s i s o f c e r v i c a l
vertebrates, while the immature stages or the
lymphadenopathy was made. Needle aspiration cytology
microfilaria prefer the blood and the lymph vessels .
was advised. On FNAC a thin thread like white worm was
Nitte University Journal of Health Science
infections are being reported. Though man is not a
suitable host, there are reports of the infective larvae
The worm was thin, thread like, cylindrical measuring
developing into adult worm and in exceptional cases
9cms long and 497um wide with rounded anterior end
even producing blood circulating microfilaria .
and tapering posterior end. On glycerin wet mount the
worm revealed thick cuticle with longitudinal ridges.
Identification of D.repens is made by studying the
Muscles were separated into dorsal and ventral bands.
morphology of the worm. An adult male worm is 5-7cm
The thick cuticle had prominent longitudinal ridges with
long and 370-450µm wide with 2-6 pre anal papillae on
fine transverse striations (Figure 2). The body cavity
the right side and 4-5 on the left. The spicules are
showed elongated esophagus and uterus with small
unequal. The left spicule is 460-590µm and right ones are
round structures within the uterus, which were the
180-210µm. The female are 10-17cm long and 460-
immature eggs. The worm was unfertilized or immature.
650µm wide with a vulva 1.15-1.62 cm from the anterior
The posterior end was tapering and unremarkable.
end. The microfilaria is unsheathed and occurs in the sub
Based on size, cuticular and internal morphology, the
cutaneous lymph spaces and in the blood of natural
worm was identified as D. repens. The identity of the
worm was confirmed as immature female D. repens at
The other species of Dirofilaria reported from India are
the Veterinary Sciences College, Hebbal, Bangalore.
D.immitis and D.tenuis . However, D.immitis can be
Routine hematological and biochemical test results were
differentiated from D.repens by the absence of
normal and no microfilaria was seen in peripheral
longitudinal ridges and transverse striations . Many
parasitologists believe that D. tenuis is restricted to USA
and consider that D. tenuis is synonymous with
D.repens . In the natural hosts, like dogs, studies have
Dirofilariasis is often reported from European countries
reported parasitemia varying from 12-37% .
surrounding the Mediterranean particularly from Italy.
The first D.repens case is said to have been reported by
Simple extraction of the worm or surgical excision of the
Angelo Pace in Palermo in 1867 . In India, sub cutaneous
lesion is the treatment of choice for human dirofilariasis.
dirofilariasis is rare, only few cases having been reported
There is seldom a need for chemotherapy as
from Kerala and most of the documented cases of
Microfilaraemia is extremely rare. In a small number of
human dirofilariasis recorded in India presented with
cases, ivermectin and/or diethylcarbamazine has been
ocular infections, affecting the eyelid, periorbital region
tried with good results. The symbiosis of filarial
and occasionally the sub conjunctivae. .
nematodes and intracellular bacteria, Wolbachia, has
been recently exploited as a target for antibiotic therapy
Dirofilaria repens infection, rarely seen in humans, is a
of filariasis. Antibiotic treatment of filarial nematode
zoonotic illness. Humans get infected through blood
results in sterility and inhibits larval development. In the
sucking arthropods such as mosquitoes, fleas and ticks.
first trial on human onchocerciasis, depletion of bacteria
For D. repens, the human body is not an appropriate
following treatment with doxycycline resulted in a
host, and therefore, no mature stages of the parasite are
complete and long term block of embryogenesis .
found in man . With changing host, agent and
environmental factors, an increasing number of human
Nitte University Journal of Health Science
molecular techniques like multilocus analysis of gene
Human cases of dirofilariasis are most probably under
enzyme system and PCR. However these tests are not
reported because many of them remain undiagnosed or
available for routine diagnostic purpose. Diagnostic
unpublished. The current case was diagnosed as
constraints and lack of awareness often result in under
subcutaneous Dirofilariasis based on parasitological
reporting of cases. Awareness and high degree of
observation. Definitive diagnosis can be made by
suspicion is the key to diagnosing human Dirofilariasis.
Figure 1- Clinical presentation of swelling
- Immature female worm of Dirofilaria repens in wet
mount showing (1) Thick cuticle (2) Intestine (3) Posterior end
(4) Thick muscular coat with longitudinal ridges and transverse
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Key Features of Palliative Care for Patients with Common Life Threatening Illnesses The following pages contain some general comments about some of the palliative care issues that may be encountered by people suffering from the end stages of some of the more common disease processes. All people are different and even people with the same diagnosis may experience different problems on thei